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Showing papers on "Colossal magnetoresistance published in 2020"


Journal ArticleDOI
TL;DR: An overview of the state of art in the studies on the fabrication, structural characterization, physical properties, and functional applications of rare earth-doped perovskite manganite oxide nanostructures is given.
Abstract: Perovskite manganites exhibit a broad range of structural, electronic, and magnetic properties, which are widely investigated since the discovery of the colossal magnetoresistance effect in 1994. As compared to the parent perovskite manganite oxides, rare earth-doped perovskite manganite oxides with a chemical composition of LnxA1-xMnO3 (where Ln represents rare earth metal elements such as La, Pr, Nd, A is divalent alkaline earth metal elements such as Ca, Sr, Ba) exhibit much diverse electrical properties due to that the rare earth doping leads to a change of valence states of manganese which plays a core role in the transport properties. There is not only the technological importance but also the need to understand the fundamental mechanisms behind the unusual magnetic and transport properties that attract enormous attention. Nowadays, with the rapid development of electronic devices toward integration and miniaturization, the feature sizes of the microelectronic devices based on rare earth-doped perovskite manganite are down-scaled into nanoscale dimensions. At nanoscale, various finite size effects in rare earth-doped perovskite manganite oxide nanostructures will lead to more interesting novel properties of this system. In recent years, much progress has been achieved on the rare earth-doped perovskite manganite oxide nanostructures after considerable experimental and theoretical efforts. This paper gives an overview of the state of art in the studies on the fabrication, structural characterization, physical properties, and functional applications of rare earth-doped perovskite manganite oxide nanostructures. Our review first starts with the short introduction of the research histories and the remarkable discoveries in the rare earth-doped perovskite manganites. In the second part, different methods for fabricating rare earth-doped perovskite manganite oxide nanostructures are summarized. Next, structural characterization and multifunctional properties of the rare earth-doped perovskite manganite oxide nanostructures are in-depth reviewed. In the following, potential applications of rare earth-doped perovskite manganite oxide nanostructures in the fields of magnetic memory devices and magnetic sensors, spintronic devices, solid oxide fuel cells, magnetic refrigeration, biomedicine, and catalysts are highlighted. Finally, this review concludes with some perspectives and challenges for the future researches of rare earth-doped perovskite manganite oxide nanostructures.

77 citations


Journal ArticleDOI
24 Jul 2020
TL;DR: In this article, the authors investigated antiferromagnetic Eu5In2Sb6, a nonsymmorphic Zintl phase, and showed that it is remarkably insulating and exhibits an exceptionally large negative magnetoresistance.
Abstract: Here we investigate antiferromagnetic Eu5In2Sb6, a nonsymmorphic Zintl phase. Our electrical transport data show that Eu5In2Sb6 is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which is consistent with the presence of magnetic polarons. From ab initio calculations, the paramagnetic state of Eu5In2Sb6 is a topologically nontrivial semimetal within the generalized gradient approximation (GGA), whereas an insulating state with trivial topological indices is obtained using a modified Becke−Johnson potential. Notably, GGA + U calculations suggest that the antiferromagnetic phase of Eu5In2Sb6 may host an axion insulating state. Our results provide important feedback for theories of topological classification and highlight the potential of realizing clean magnetic narrow-gap semiconductors in Zintl materials.

35 citations


Journal ArticleDOI
TL;DR: In this paper, different homo- and hetero-epitaxial interfaces with extraordinary structural quality and different functionalities, including high-temperature superconductivity, thermoelectricity, and magnetism, are presented.
Abstract: Complex oxides provide a versatile playground for many phenomena and possible applications, for instance, high-temperature superconductivity, magnetism, ferroelectricity, metal-to-insulator transition, colossal magnetoresistance, and piezoelectricity. The origin of these phenomena is the competition between different degrees of freedom such as charge, orbital, and spin, which are interrelated with the crystal structure, the oxygen stoichiometry, and the doping dependence. Recent developments not only in the epitaxial growth technologies, such as reactive molecular beam epitaxy, but also in the characterization techniques, as aberration-corrected scanning transmission electron microscopy with spectroscopic tools, allow synthesizing and identifying epitaxial systems at the atomic scale. Combination of different oxide layers opens access to interface physics and leads to engineering interface properties, where the degrees of freedom can be artificially modified. In this review, we present different homo- and hetero-epitaxial interfaces with extraordinary structural quality and different functionalities, including high-temperature superconductivity, thermoelectricity, and magnetism.

30 citations


Journal ArticleDOI
TL;DR: Systematic studies of the MR of single-layer graphene on various oxide- and non-oxide-based terraced surfaces demonstrate that the terraced structure is the dominant factor driving the MR enhancement, which opens a new route for tailoring the physical property of 2D materials by engineering the strain through a terraced substrate.
Abstract: Disorder-induced magnetoresistance (MR) effect is quadratic at low perpendicular magnetic fields and linear at high fields. This effect is technologically appealing, especially in 2D materials such as graphene, since it offers potential applications in magnetic sensors with nanoscale spatial resolution. However, it is a great challenge to realize a graphene magnetic sensor based on this effect because of the difficulty in controlling the spatial distribution of disorder and enhancing the MR sensitivity in the single-layer regime. Here, a room-temperature colossal MR of up to 5000% at 9 T is reported in terraced single-layer graphene. By laminating single-layer graphene on a terraced substrate, such as TiO2 -terminated SrTiO3 , a universal one order of magnitude enhancement in the MR compared to conventional single-layer graphene devices is demonstrated. Strikingly, a colossal MR of >1000% is also achieved in the terraced graphene even at a high carrier density of ≈1012 cm-2 . Systematic studies of the MR of single-layer graphene on various oxide- and non-oxide-based terraced surfaces demonstrate that the terraced structure is the dominant factor driving the MR enhancement. The results open a new route for tailoring the physical property of 2D materials by engineering the strain through a terraced substrate.

26 citations


Posted Content
09 Mar 2020
TL;DR: This work demonstate a non-equilibrium route for ultrafast modification of Fermi surface topology in quantum materials and demonstrates that this nonequilibrium topological electronic transition finds its microscopic origin in the dynamical modification of the effective electronic correlations.
Abstract: Fermi surface is at the heart of our understanding of metals and strongly correlated many-body systems. An abrupt change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. While Lifshitz transitions have been demonstrated for a broad range of materials and using different types of static external perturbations such as strain, doping, pressure and temperature, a non-equilibrium route toward ultrafast and transient modification of the Fermi surface topology has not been experimentally demonstrated. Combining time-resolved multidimensional photoemission spectroscopy with state-of-the-art TDDFT+U simulations, we introduce a scheme for driving an ultrafast Lifshitz transition in the correlated Weyl semimetal T$\mathrm{_{d}}$-MoTe$_{2}$. We demonstrate that this non-equilibrium topological electronic transition finds its microscopic origin in the dynamical modification of the effective electronic correlations. These results shed light on a novel ultrafast and all-optical scheme for controlling the Fermi surface topology in correlated quantum materials.

25 citations



Journal ArticleDOI
TL;DR: In this article, the phenomenon of colossal magnetoresistance (CMR) was revived, where the magnetoreistance can attend higher orders of ma..., and the magnetororesistance can attract much attention.
Abstract: Manganese-based perovskite oxides have attracted much attention since the phenomenon of colossal magnetoresistance (CMR) was revived, where the magnetoresistance (MR) can attend higher orders of ma...

12 citations


Journal ArticleDOI
01 Oct 2020-Small
TL;DR: It is expected that other oxide perovskite thin films will also yield similar structural environments with variation of OOR patterns, and thereby provide promising opportunities for atomic scale control of material properties through strain engineering.
Abstract: ABO3 perovskite materials and their derivatives have inherent structural flexibility due to the corner sharing network of the BO6 octahedron, and the large variety of possible structural distortions and strong coupling between lattice and charge/spin degrees of freedom have led to the emergence of intriguing properties, such as high-temperature superconductivity, colossal magnetoresistance, and improper ferroelectricity. Here, an unprecedented polar ferromagnetic metal phase in SrRuO3 (SRO) thin films is presented, arising from the strain-controlled oxygen octahedral rotation (OOR) pattern. For compressively strained SRO films grown on SrTiO3 substrate, oxygen octahedral network relaxation is accompanied by structural phase separation into strained tetragonal and bulk-like orthorhombic phases, and the asymmetric OOR evolution across the phase boundary allows formation of the polar phase, while bulk metallic and ferromagnetic properties are maintained. From the results, it is expected that other oxide perovskite thin films will also yield similar structural environments with variation of OOR patterns, and thereby provide promising opportunities for atomic scale control of material properties through strain engineering.

10 citations


Journal ArticleDOI
TL;DR: In this article, a single-crystal van der Waals layered material was shown to exhibit the Baber law in a wide temperature range up to 120 K, indicating that the electron-electron scattering plays a dominant role in this material.
Abstract: A characteristic of a Fermi liquid is the ${T}^{2}$ dependence of its resistivity, sometimes referred to as the Baber law. However, for most metals, this behavior is only restricted to very low temperatures, usually below 20 K. Here, we experimentally demonstrate that for the single-crystal van der Waals layered material $\mathrm{MoOC}{\mathrm{l}}_{2}$, the Baber law holds in a wide temperature range up to \ensuremath{\sim}120 K, indicating that the electron-electron scattering plays a dominant role in this material. Combining with the specific heat measurement, we find that the modified Kadowaki-Woods ratio of the material agrees well with many other strongly correlated metals. Furthermore, in the magnetotransport measurement, a colossal magnetoresistance is observed, which reaches \ensuremath{\sim}350% at 9 T and displays no sign of saturation. With the help of first-principles calculations, we attribute this behavior to the presence of open orbits on the Fermi surface. We also suggest that the dominance of electron-electron scattering is related to an incipient charge density wave state of the material. Our results establish $\mathrm{MoOC}{\mathrm{l}}_{2}$ as a strongly correlated metal and shed light on the underlying physical mechanism, which may open a new path for exploring the effects of electron-electron interaction in van der Waals layered structures.

10 citations


Journal ArticleDOI
TL;DR: In this article, electron-phonon anomalies in LSNO were found by inelastic neutron scattering. And they were shown to be anomalous in the case of Ni-O bond-stretching modes.
Abstract: Doped antiferromagnets host a vast array of physical properties and learning how to control them is one of the biggest challenges of condensed matter physics. [Formula: see text] (LSNO) is a classic example of such a material. At low temperatures holes introduced via substitution of La by Sr segregate into lines to form boundaries between magnetically ordered domains in the form of stripes. The stripes become dynamic at high temperatures, but LSNO remains insulating presumably because an interplay between magnetic correlations and electron-phonon coupling localizes charge carriers. Magnetic degrees of freedom have been extensively investigated in this system, but phonons are almost completely unexplored. We searched for electron-phonon anomalies in LSNO by inelastic neutron scattering. Giant renormalization of plane Ni-O bond-stretching modes that modulate the volume around Ni appears on entering the dynamic charge stripe phase. Other phonons are a lot less sensitive to stripe melting. Dramatic overdamping of the breathing modes indicates that dynamic stripe phase may host small polarons. We argue that this feature sets electron-phonon coupling in nickelates apart from that in cuprates where breathing phonons are not overdamped and point out remarkable similarities with the colossal magnetoresistance manganites.

9 citations


Journal ArticleDOI
TL;DR: A newly developed hand-held magnetic field meter, which enables the measurement of the magnitude of pulsed, alternating, or permanent magnetic flux density in a range from 0.06 up to 10 T, and can be used for various industrial and scientific applications.
Abstract: This paper describes a newly developed hand-held magnetic field meter, which enables the measurement of the magnitude of pulsed, alternating, or permanent magnetic flux density in a range from 0.06 up to 10 T. The device measures the magnitude of magnetic flux density independent of the field direction (B-scalar) and its measurement frequency ranges from dc to 100 kHz. This magnetometer consists of a hand-held magnetic field measurement meter and a pluggable probe whose main element is a spintronic sensor based on the colossal magnetoresistance (CMR) phenomenon. The new design of a probe containing a temperature sensor and a CMR-B-scalar sensor made from two manganite films with different resistivity versus temperature dependences ensures a reduced response signal dependence on temperature and thus increased the accuracy of the measurements. The hand-held meter has a graphical color touch screen for the display of the waveforms and provides measurements without the use of external oscilloscopes or other analog graphing devices. This magnetometer can be used for various industrial and scientific applications such as for the investigation of high-power electrical motors, fast high electrical current transients appearing in cases of the commutation of pulsed power circuits, for the measurement of pulsed magnetic fields in magnetic coils, or for measuring the dynamics of magnetic fields during electromagnetic metal forming and welding.

Journal ArticleDOI
TL;DR: In this paper, the electrical transport and low-field magnetoresistance properties of the composites were systematically studied using small polaron hopping (SPH) and variable range hopping (VRH) models.

Journal ArticleDOI
TL;DR: This work reveals that Fe4+δSe5 with ordered Fe vacancy is a nonoxide compound with the Verwey-like electronic correlation, and is identified as the parent phase of FeSe superconductor.
Abstract: We studied the electrical transport of Fe4+δSe5 single-crystal nanowires exhibiting √5 × √5 Fe-vacancy order and mixed valence of Fe. Fe4+δSe5 compound has been identified as the parent phase of FeSe superconductor. A first-order metal-insulator (MI) transition of transition temperature TMI ∼ 28 K is observed at zero magnetic fields (B). Colossal positive magnetoresistance emerges, resulting from the magnetic field-dependent MI transition. TMI demonstrates anisotropic magnetic field dependence with the preferred orientation along the c axis. At temperature T

Journal ArticleDOI
TL;DR: In this article, the authors investigated the switchable magnetoresistance (MR) effect of the Ruddelsden-Popper (RP) oxide Ca4Mn3O10 (CMO), which shows a metal-to-insulator transition (MIT) at 70 K (TMIT).

Posted Content
TL;DR: In this article, the electron-phonon anomalies in LSNO by inelastic neutron scattering were investigated and it was shown that large renormalization of plane Ni-O bond-stretching modes appeared on entering the dynamic charge stripe phase.
Abstract: Doped antiferromagnets host a vast array of physical properties and learning how to control them is one of the biggest challenges of condensed matter physics. La$_{1.7}$Sr$_{0.3}$NiO$_4$ (LSNO) is a classic example of such a material. At low temperatures holes introduced via substitution of La by Sr segregate into lines to form boundaries between magnetically ordered domains in the form of stripes. The stripes become dynamic at high temperatures, but LSNO remains insulating presumably because an interplay between magnetic correlations and electron-phonon coupling localizes charge carriers. Magnetic degrees of freedom have been extensively investigated in this system, but phonons are almost completely unexplored. We searched for electron-phonon anomalies in LSNO by inelastic neutron scattering. Giant renormalization of plane Ni-O bond-stretching modes that modulate the volume around Ni appears on entering the dynamic charge stripe phase. Other phonons are a lot less sensitive to stripe melting. Dramatic overdamping of the breathing modes indicates that dynamic stripe phase may host small polarons. We argue that this feature sets electron-phonon coupling in nickelates apart from that in cuprates where breathing phonons are not overdamped and point out remarkable similarities with the colossal magnetoresistance (CMR) manganites.

Journal ArticleDOI
TL;DR: In this paper, four half-doped perovskite Manganese oxide (MnO3) samples with different particle sizes are prepared by high-temperature solid-state reaction and ball milling.
Abstract: Half-doped perovskite Manganese oxide has been widely studied because of its excellent properties such as colossal magnetoresistance (CMR) effect and charge-ordered (CO) phase separation. In this work, four Sm0.5Ca0.5MnO3 samples with different particle sizes are prepared by high-temperature solid-state reaction and ball milling. The crystal structure of the samples is studied by X-ray diffraction (XRD). The Sm0.5Ca0.5MnO3 sample is single phase, which belongs to orthorhombic structure. The surface morphology and particle size of the samples are examined by scanning electron microscope (SEM). The average particle size of the sample without ball milling is about 4 μm. With ball milling time for 12 h, 24 h, and 36 h, the particle size decreases, and finally it reaches hundreds to tens of nanometers. This shows that ball milling is an effective way to control the particle size. The M–T curves and M–H hysteresis loops of the samples are measured by physical properties measurements systems (PPMS). The two M–T curves measured in the warming and cooling processes do not overlap for Sm0.5Ca0.5MnO3 without ball milling, and the phenomenon of thermal hysteresis appears. Meanwhile, the M–T curve has a significant protuberance peak near 270 K. All of these indicate the CO behavior, whereas the particle size of Sm0.5Ca0.5MnO3 decreases with different milling times (12–36 h) and the CO phase is suppressed gradually, which leads to the decrease of CO temperature, magnetization, remanence, and coercivity.

Journal ArticleDOI
01 Mar 2020
TL;DR: In this article, the Andreev reflection and the interband Klein tunneling couple electronlike and hole-like states through the action of either a superconducting pair potential or an electrostatic potential.
Abstract: Unlike the more common local conductance spectroscopy, nonlocal conductance can differentiate between nontopological zero-energy modes localized around inhomogeneities, and true Majorana edge modes in the topological phase. In particular, negative nonlocal conductance is dominated by the crossed Andreev reflection. Fundamentally, the effect reflects the system's topology. In graphene, the Andreev reflection and the inter-band Klein tunneling couple electronlike and hole-like states through the action of either a superconducting pair potential or an electrostatic potential. We are here probing quantum phenomena in modified graphitic samples. Four-point contact transport measurements at cryogenic to room temperatures were conducted using a Quantum Design Physical Property Measurement System. The observed negative nonlocal differential conductance Gdiff probes the Andreev reflection at the walls of the superconducting grains coupled by Josephson effect through the semiconducting matrix. In addition, Gdiff shows the butterfly shape that is characteristic to resistive random-access memory devices. In a magnetic field, the Andreev reflection counters the effect of the otherwise lowered conduction. At low temperatures, the magnetoresistance shows irreversible yet strong giant oscillations that are known to be quantum in nature. In addition, we have found evidence for seemingly granular superconductivity. Thus, graphitic materials show potential for quantum electronics applications, including rectification and topological states.

Journal ArticleDOI
TL;DR: The results demonstrate that the superexchange interactions are finely balanced in Sr2Mn2.77As2O2, and there is no evidence of MR.
Abstract: Several different mechanisms of magnetoresistance (MR) have been observed in 1111 LnMnAsO1–xFx oxypnictides (Ln = lanthanide) as a result of magnetic coupling between the Mn and Ln. Such phases als...

Journal ArticleDOI
TL;DR: In this paper, spatial confinement is used to tune the level of quenched disorder in a complex-oxide system while leaving other physical variables largely undisturbed, such as local lattice distortions and electronic and magnetic environments.
Abstract: Complex oxides have rich functionalities and advantages for future technologies. In many systems, quenched disorder often holds the key to determine their physical properties, and these properties can be further tuned by chemical doping. However, understanding the role of quenched disorder is complicated because chemical doping simultaneously alters other physical variables such as local lattice distortions and electronic and magnetic environments. Here, we show that spatial confinement is an effective approach to tuning the level of quenched disorder in a complex-oxide system while leaving other physical variables largely undisturbed. Through the confinement of a manganite system down to quasi-one-dimensional nanowires, we observed that the nature of its metal-insulator phase transition exhibits a crossover from a discontinuous to a continuous characteristic, in close accordance with quenched disorder theories. We argue that the quenched disorder, finite size, and surface effects all contribute to our experimental observations. Noticeably, with reduced nanowire width, the magnetoresistance shows substantial enhancement at low temperatures. Our findings offer new insight into experimentally tuning the quenched disorder effect to achieve novel functionalities at reduced dimensions.

Journal ArticleDOI
TL;DR: In this article, a magnetic-field-driven metal-insulator transition (MIT) was observed in a magnetic semiconductor and the authors ascribe this striking MIT as a field-driven transition from an antiferromagnetic and paramagnetic insulator to a spin-polarized topological semimetal.
Abstract: Metal-insulator transition (MIT) is one of the most conspicuous phenomena in correlated electron systems. However such transition has rarely been induced by an external magnetic field as the field scale is normally too small compared with the charge gap. In this paper we present the observation of a magnetic-field-driven MIT in a magnetic semiconductor $\beta $-EuP$_3$. Concomitantly, we found a colossal magnetoresistance (CMR) in an extreme way: the resistance drops billionfold at 2 kelvins in a magnetic field less than 3 teslas. We ascribe this striking MIT as a field-driven transition from an antiferromagnetic and paramagnetic insulator to a spin-polarized topological semimetal, in which the spin configuration of $\mathrm{Eu^{2+}}$ cations and spin-orbital coupling (SOC) play a crucial role. As a phosphorene-bearing compound whose electrical properties can be controlled by the application of field, $\beta $-EuP$_3$ may serve as a tantalizing material in the basic research and even future electronics.

Journal ArticleDOI
TL;DR: In this article, the spin-polaron and orientation conductivity mechanisms of single-crystal La1.2Sr1.8Mn2O7 were studied experimentally and theoretically in the 75-300 K temperature range in magnetic fields varying in intensity from 0 to 90 kOe.
Abstract: The resistance of single-crystal La1.2Sr1.8Mn2(1 – z)O7 is studied experimentally and theoretically in the 75–300 K temperature range in magnetic fields varying in intensity from 0 to 90 kOe. The magnetoresistance is governed by spin-polaron and orientation conductivity mechanisms. The observed magnetoresistance of La1.2Sr1.8Mn2O7 at 75–300 K is characterized using the method of separation of contributions from different conductivity mechanisms. The calculated and experimental data agree closely. Temperature dependences of the spin-polaron size (in relative units) are calculated in the 75–300 K interval in zero magnetic field and in a 90 kOe field. It is demonstrated that the increasing (along the magnetic field) spin-polaron linear size gives rise to colossal magnetoresistance. In other words, the size change of magnetic inhomogeneities produces the primary contribution to the colossal magnetoresistance value.

Journal ArticleDOI
TL;DR: In this article, the spin-polaron conduction mechanism was used to determine the magnetoresistance of a single crystal in magnetic fields from 0 to 90 kOe in the ferromagnetic temperature range.
Abstract: We have analyzed the resistance of La1.2Sr1.8Mn2(1 – z)O7 single crystal in magnetic fields from 0 to 90 kOe in the ferromagnetic temperature range. The observed magnetoresistance of La1.2Sr1.8Mn2O7 is described based on the spin-polaron conduction mechanism. The magnetoresistance is determined by the change in the sizes and magnetic moment directions of magnetic inhomogeneities (polarons). It is shown that the colossal magnetoresistance is ensured by an increase (along the magnetic field) of the polaron linear size. It is found using the method for separating the contributions of different conduction mechanisms to the magnetoresistance that the contribution to the magnetoresistance from the orientation mechanism at 80 K in low magnetic fields is close to 50%. With increasing magnetic field, this contribution decreases and becomes small in fields exceeding 30 kOe. The comparable contributions to the conductivity from the orientational and spin-polaron mechanisms unambiguously necessitate the inclusion of both conduction mechanisms in the magnetoresistance calculations. We have calculated the temperature variation of the polaron size (in relative units) in zero magnetic field and in a magnetic field of 90 kOe.

Journal ArticleDOI
TL;DR: In this paper, perturbed angular correlation (PAC) was used to measure hyperfine interactions at La and Mn sites of LaMnO3+δ(δ ∼ 0.15) using 140Ce and 111Cd at La sites as probe nuclei in order to investigate within an atomic scale the magnetic and electric interactions in this compound.
Abstract: LaMnO3+δ is a complex oxide, which, depending on the oxygen excess concentration, presents different crystalline structure and interesting magnetic and electric properties such as colossal magnetoresistance, polaron dynamics, multiferroic behavior, and charge-orbital ordering. This complexity requires different characterization techniques to draw a picture as complete as possible allowing a good understanding of these phenomena. Here, we have used the perturbed angular correlation (PAC) technique to measure hyperfine interactions at La and Mn sites of LaMnO3+δ(δ ∼0.15) using 140Ce and 111Cd at La sites as probe nuclei in order to investigate within an atomic scale the magnetic and electric interactions in this compound. The results show that 111Cd nuclei occupy highly symmetric local sites in agreement with a rhombohedral structure. The magnetic hyperfine field (Bhf) measured with 111Cd at La sites is very small (Bhf = 0.40 T) due to the supertransferred magnetic field from Mn neighbors through oxygen orbitals. On the other hand, 140Ce nuclei at La sites present a saturation field of around 3.7 T much higher than that expected for La sites (due to the weak transfer field by superexchange mechanism). In addition, for temperature range above the magnetic ordering (200-300 K) a dynamic hyperfine interaction was observed characterized by the attenuation parameter λ(T) whose temperature dependence allowed to determine the activation energy (Ea) associated to charge transfer. The polarization of the 4f-electron of Ce impurities affects the local magnetic field at impurity sites as well as the Ea.

Journal ArticleDOI
TL;DR: In this article, doping dependent modifications in the microstructure polycrystalline La0.3Mn1-xTixO3 (LSMTO) (x = 0.03, 0.06 and 0.12) compounds were discussed in detail.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the dynamic control of two entirely different phases (canted G-type antiferromagnetic metal and C-type charge/orbital ordered insulator phase) in an electron-doped system Ca1−xCexMnO3 (x = 0.05).
Abstract: The coexistence of distinct insulating and metallic phases within the same manganite sample, i.e., phase separation scenario, provides an excellent platform for tailoring the complex electronic and magnetic properties of strongly correlated materials. Here, based on an electric-double-layer transistor configuration, we demonstrate the dynamic control of two entirely different phases—canted G-type antiferromagnetic metal and C-type antiferromagnetic charge/orbital ordered insulator phase—in electron-doped system Ca1−xCexMnO3 (x = 0.05). The reversible metal-to-insulator transition, enhanced colossal magnetoresistance (∼ 27 000% for Vg = 3.0 V), and giant memory effect have been observed, which can be attributed to an electronic phase separation scenario manipulated by a tiny doping-level-variation of less than 0.02 electrons per formula unit. In addition, the controllable multi-resistance states by the combined application of magnetic and electrostatic fields may serve as an indicator to probe the dynamic multiphase competition of strongly correlated oxides. These results offer crucial information to understand the physical nature of phase separation phenomena in manganite systems.

Posted Content
TL;DR: In this paper, the authors investigated antiferromagnetic Eu$5}$In$2}$Sb$6}, a nonsymmorphic Zintl phase.
Abstract: Here we investigate antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$, a nonsymmorphic Zintl phase. Our electrical transport data show that Eu$_{5}$In$_{2}$Sb$_{6}$ is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which is consistent with the presence of magnetic polarons. From {\it ab initio} calculations, the paramagnetic state of Eu$_{5}$In$_{2}$Sb$_{6}$ is a topologically nontrivial semimetal within the generalized gradient approximation (GGA), whereas an insulating state with trivial topological indices is obtained using a modified Becke-Johnson potential. Notably, GGA+U calculations suggest that the antiferromagnetic phase of Eu$_{5}$In$_{2}$Sb$_{6}$ may host an axion insulating state. Our results provide important feedback for theories of topological classification and highlight the potential of realizing clean magnetic narrow-gap semiconductors in Zintl materials.

Posted Content
TL;DR: In this paper, it was shown that the Baber law holds in a wide temperature range up to ~120 K, indicating that the electron-electron scattering plays a dominant role in this material.
Abstract: A characteristic of a Fermi liquid is the T^2 dependence of its resistivity, sometimes referred to as the Baber law. However, for most metals, this behavior is only restricted to very low temperatures, usually below 20 K. Here, we experimentally demonstrate that for the single-crystal van der Waals layered material MoOCl2, the Baber law holds in a wide temperature range up to ~120 K, indicating that the electron-electron scattering plays a dominant role in this material. Combining with the specific heat measurement, we find that the modified Kadowaki-Woods ratio of the material agrees well with many other strongly correlated metals. Furthermore, in the magneto-transport measurement, a colossal magneto-resistance is observed, which reaches ~350% at 9 T and displays no sign of saturation. With the help of first-principles calculations, we attribute this behavior to the presence of open orbits on the Fermi surface. We also suggest that the dominance of electron-electron scattering is related to an incipient charge density wave state of the material. Our results establish MoOCl2 as a strongly correlated metal and shed light on the underlying physical mechanism, which may open a new path for exploring the effects of electron-electron interaction in van der Waals layered structures.

Journal ArticleDOI
TL;DR: In this paper, it was shown that if the thickness of the tube wall is significantly less than Bean's penetration length, the nonlinear magnetic field diffusion equation describing the field propagation process inside the tube can be replaced by a simplified lumped-parameter equation.
Abstract: In this work, we present an investigation of transient magnetic field behavior in thin-walled superconducting tubes. It has been determined that if the thickness of the tube wall is significantly less than Bean’s penetration length, the non-linear magnetic field diffusion equation describing the field propagation process inside the tube can be replaced by a simplified lumped-parameter equation. This makes it possible to quickly calculate the current induced in the tube wall and the magnetic field penetrated in the tube cavity. In order to validate this theory, an experimental study of transient magnetic field penetration into a Pb-doped B-2223 ( Bi 1.8 Pb 0.26 Sr 2 Ca 2 Cu 3 O 10 + x) tube was conducted. This was done at the temperature of liquid nitrogen using a search coil (B-dot) and a miniature colossal magnetoresistance (CMR)-B-scalar magnetic field sensor made from manganite films, which exhibit a CMR phenomenon. The experimental results were then compared with the datasheet of the superconducting tube manufacturer and the 2D axisymmetric finite element model. It was demonstrated that combining the measurements of the magnetic field outside and inside the tube with the lumped-parameter description allows one to obtain the following information: the screened and trapped magnetic field, the critical current density vs the magnetic field dependence, and the power law index of the superconducting tube material. This enables the development of a fast, non-destructive method for testing the quality of superconducting tubular current leads.

Journal ArticleDOI
TL;DR: In this paper, the structural, transport and magnetic properties of Nd0.7−xLaxSr0.3MnO3 samples were investigated and the correlated polaron hopping model was used to describe the transport properties of La-substituted manganite.
Abstract: The structural, transport and magnetic properties of Nd0.7−xLaxSr0.3MnO3 (for x = 0.0, 0.1, 0.2, 0.3) manganite prepared by solid-state route were investigated. All the samples are exhibiting distorted orthorhombic perovskite structure. Lattice parameters and bond angles are increasing with an increase in La concentration. The electrical resistivity ρ(T → 0) and ρ(Tc), both are decreasing with substitution of La (x = 0.0, 0.1, 0.2, 0.3) and the presence of an external magnetic field giving rise to the colossal magnetoresistance (CMR) effect. The temperature-dependent transport nature has been explored with a correlated polaron hopping mechanism based on the Holstein Hamiltonian model. This model is very well concurring with our experimental results and it is further addressing the widely known transition from the low-temperature metallic to the localized polaron hopping conductivity at high temperature. Furthermore, the spin-order temperature (Tc) and the atomic-order temperature (Tca) both are increasing with La substitution. The present analysis shows that the correlated polaron hopping model describes the transport properties of La-substituted Nd0.7−xLaxSr0.3MnO3 samples.