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Showing papers on "Colossal magnetoresistance published in 2022"


Journal ArticleDOI
TL;DR: In this article , a formalism was introduced to resolve the question of the physics of the metal-insulator transitions in the rare-earth perovskite nickelates (R NiO 3 ) and Ruddlesden-Popper calcium ruthenates (Ca 2 RuO 4 ) in bulk, heterostructure, and epitaxially strained thin film forms, finding that electron-lattice coupling is key to stabilizing the insulating state in both classes of materials.
Abstract: Abstract Many materials exhibit phase transitions at which both the electronic properties and the crystal structure change. Some authors have argued that the change in electronic order is primary, with the lattice distortion a relatively minor side-effect, and others have argued that the lattice distortions play an essential role in the energetics of the transition. In this paper, we introduce a formalism that resolves this long-standing problem. The methodology works with any electronic structure method that produces solutions of the equation of state determining the electronic order parameter as a function of lattice distortion. We use the formalism to settle the question of the physics of the metal–insulator transitions in the rare-earth perovskite nickelates ( R NiO 3 ) and Ruddlesden–Popper calcium ruthenates (Ca 2 RuO 4 ) in bulk, heterostructure, and epitaxially strained thin film forms, finding that electron-lattice coupling is key to stabilizing the insulating state in both classes of materials.

15 citations


Journal ArticleDOI
TL;DR: In this article , a formalism was introduced to resolve the question of the physics of the metal-insulator transitions in the rare-earth perovskite nickelates (R NiO 3 ) and Ruddlesden-Popper calcium ruthenates (Ca 2 RuO 4 ) in bulk, heterostructure, and epitaxially strained thin film forms, finding that electron-lattice coupling is key to stabilizing the insulating state in both classes of materials.
Abstract: Abstract Many materials exhibit phase transitions at which both the electronic properties and the crystal structure change. Some authors have argued that the change in electronic order is primary, with the lattice distortion a relatively minor side-effect, and others have argued that the lattice distortions play an essential role in the energetics of the transition. In this paper, we introduce a formalism that resolves this long-standing problem. The methodology works with any electronic structure method that produces solutions of the equation of state determining the electronic order parameter as a function of lattice distortion. We use the formalism to settle the question of the physics of the metal–insulator transitions in the rare-earth perovskite nickelates ( R NiO 3 ) and Ruddlesden–Popper calcium ruthenates (Ca 2 RuO 4 ) in bulk, heterostructure, and epitaxially strained thin film forms, finding that electron-lattice coupling is key to stabilizing the insulating state in both classes of materials.

12 citations


Journal ArticleDOI
TL;DR: In this article , an exotic quantum state that is driven by ab plane chiral orbital currents (COC) flowing along edges of MnTe6 octahedra is reported.
Abstract: Colossal magnetoresistance (CMR) is an extraordinary enhancement of the electrical conductivity in the presence of a magnetic field. It is conventionally associated with a field-induced spin polarization that drastically reduces spin scattering and electric resistance. Ferrimagnetic Mn3Si2Te6 is an intriguing exception to this rule: it exhibits a seven-order-of-magnitude reduction in ab plane resistivity that occurs only when a magnetic polarization is avoided1,2. Here, we report an exotic quantum state that is driven by ab plane chiral orbital currents (COC) flowing along edges of MnTe6 octahedra. The c axis orbital moments of ab plane COC couple to the ferrimagnetic Mn spins to drastically increase the ab plane conductivity (CMR) when an external magnetic field is aligned along the magnetic hard c axis. Consequently, COC-driven CMR is highly susceptible to small direct currents exceeding a critical threshold, and can induce a time-dependent, bistable switching that mimics a first-order ‘melting transition’ that is a hallmark of the COC state. The demonstrated current-control of COC-enabled CMR offers a new paradigm for quantum technologies. Current-control of chiral orbital current-enabled colossal magnetoresistance offers a new paradigm for quantum technologies.

10 citations


Journal ArticleDOI
TL;DR: In this paper , the authors discuss the recent advancements in describing, understanding and application of electron-doped rare earth nickelates and conclude with a discussion of the developments and outlook for harnessing the quantum functional properties of nickelates in novel devices for sensing and neuromorphic computation.
Abstract: The family of rare earth (RE) nickelate perovskites RENiO3 has emerged over the past two decades as an important platform for quantum matter physics and advanced applications. The parent compounds from this family are strongly correlated insulators or metals, in most cases with long-range spin order. In the past few years, carrier doping has been achieved using different approaches and has been proven to be a powerful tuning parameter for the microscopic properties and collective macroscopic states in RENiO3 compounds. In particular, a series of recent studies has shown that carrier doping can be responsible for dramatic but reversible changes in the long-range electronic and magnetic properties, underscoring the potential for use of nickelates in advanced functional devices. In this review, we discuss the recent advancements in our description, understanding and application of electron-doped rare earth nickelates. We conclude with a discussion of the developments and outlook for harnessing the quantum functional properties of nickelates in novel devices for sensing and neuromorphic computation.

6 citations


Journal ArticleDOI
01 Jan 2022-Sensors
TL;DR: It was demonstrated that Mn excess Mn/(La + Sr) = 1.21 increases the metal-insulator transition temperature of the films up to 285 K, allowing the increase in the operation temperature of magnetic sensors up to 363 K, which allows to fabricate CMR sensors with predetermined parameters in a wide range of magnetic fields and temperatures.
Abstract: The results of colossal magnetoresistance (CMR) properties of La0.83Sr0.17Mn1.21O3 (LSMO) films grown by pulsed injection MOCVD technique onto various substrates are presented. The films with thicknesses of 360 nm and 60 nm grown on AT-cut single crystal quartz, polycrystalline Al2O3, and amorphous Si/SiO2 substrates were nanostructured with column-shaped crystallites spread perpendicular to the film plane. It was found that morphology, microstructure, and magnetoresistive properties of the films strongly depend on the substrate used. The low-field MR at low temperatures (25 K) showed twice higher values (−31% at 0.7 T) for LSMO/quartz in comparison to films grown on the other substrates (−15%). This value is high in comparison to results published in literature for manganite films prepared without additional insulating oxides. The high-field MR measured up to 20 T at 80 K was also the highest for LSMO/quartz films (−56%) and demonstrated the highest sensitivity S = 0.28 V/T at B = 0.25 T (voltage supply 2.5 V), which is promising for magnetic sensor applications. It was demonstrated that Mn excess Mn/(La + Sr) = 1.21 increases the metal-insulator transition temperature of the films up to 285 K, allowing the increase in the operation temperature of magnetic sensors up to 363 K. These results allow us to fabricate CMR sensors with predetermined parameters in a wide range of magnetic fields and temperatures.

6 citations


Journal ArticleDOI
TL;DR: In this article , the authors reported the emergence of unusual, thickness-dependent properties in ultrathin CaRuO 3 films by insertion of a single isovalent SrO layer (referred to as δ-doping).
Abstract: Abstract Heterostructures of complex transition metal oxides are known to induce extraordinary emergent quantum states that arise from broken symmetry and other discontinuities at interfaces. Here we report the emergence of unusual, thickness-dependent properties in ultrathin CaRuO 3 films by insertion of a single isovalent SrO layer (referred to as δ-doping). While bulk CaRuO 3 is metallic and nonmagnetic, films thinner than or equal to ~15-unit cells (u.c.) are insulating though still nonmagnetic. However, δ-doping to middle of such CaRuO 3 films induces an insulator-to-metal transition and unusual ferromagnetism with strong magnetoresistive behavior. Atomically resolved imaging and density-functional-theory calculations reveal that the whole δ-doped film preserves the bulk-CaRuO 3 orthorhombic structure, while appreciable structural and electronic changes are highly localized near the SrO layer. The results highlight delicate nature of magnetic instability in CaRuO 3 and subtle effects that can alter it, especially the role of A-site cation in electronic and magnetic structure additional to lattice distortion in ruthenates. It also provides a practical approach to engineer material systems via highly localized modifications in their structure and composition that may offer new routes to the design of oxide electronics.

6 citations


Journal ArticleDOI
TL;DR: In this article , high-quality La0.67Ca0.33Mn0.97Co0.03O3 polycrystalline ceramics were prepared by the sol-gel method and the results showed that Ag doping has important impact on metal-insulator and ferromagnetic-paramagnetic transitions.

6 citations


Journal ArticleDOI
TL;DR: In this article , a high-temperature substantial magnetoresistance (MR) in a La0.67Sr0.33MnO3 (LSMO) film grown on a piezoelectric substrate is reported.

5 citations


Journal ArticleDOI
TL;DR: Based on the analysis of crystal structure, Mn3+/Mn4+ pairs, distortion of MnO6 octahedron, and electrical transport properties of La1-xCaxMnO3 and La 1-xSrxMmO3 materials, room-temperature coefficient of resistivity (TCR) of La0.7Ca0.18Sr0.12Mn O3 films was optimized by Ca/Sr co-doping at the A-site as mentioned in this paper .

4 citations


Journal ArticleDOI
TL;DR: In this article, the influence of Co doping on electrical and magnetic properties of polycrystalline ceramics is systematically studied and the results reveal that the TCR and magnetoresistance can be optimized by tuning the Co content.

4 citations


Journal ArticleDOI
25 May 2022-Sensors
TL;DR: In this article , the results of colossal magnetoresistance (CMR) properties of La1-xSrxMnyO3 (LSMO) films grown by the pulsed injection MOCVD technique onto an Al2O3 substrate are presented.
Abstract: The results of colossal magnetoresistance (CMR) properties of La1-xSrxMnyO3 (LSMO) films grown by the pulsed injection MOCVD technique onto an Al2O3 substrate are presented. The grown films with different Sr (0.05 ≤ x ≤ 0.3) and Mn excess (y > 1) concentrations were nanostructured with vertically aligned column-shaped crystallites spread perpendicular to the film plane. It was found that microstructure, resistivity, and magnetoresistive properties of the films strongly depend on the strontium and manganese concentration. All films (including low Sr content) exhibit a metal–insulator transition typical for manganites at a certain temperature, Tm. The Tm vs. Sr content dependence for films with a constant Mn amount has maxima that shift to lower Sr values with the increase in Mn excess in the films. Moreover, the higher the Mn excess concentration in the films, the higher the Tm value obtained. The highest Tm values (270 K) were observed for nanostructured LSMO films with x = 0.17–0.18 and y = 1.15, while the highest low-field magnetoresistance (0.8% at 50 mT) at room temperature (290 K) was achieved for x = 0.3 and y = 1.15. The obtained low-field MR values were relatively high in comparison to those published in the literature results for lanthanum manganite films prepared without additional insulating oxide phases. It can be caused by high Curie temperature (383 K), high saturation magnetization at room temperature (870 emu/cm3), and relatively thin grain boundaries. The obtained results allow to fabricate CMR sensors for low magnetic field measurement at room temperature.

Journal ArticleDOI
TL;DR: In this paper , the effects of K+ substitution at the Ba-site on the structural, magnetic, and electrical properties and magnetoresistance of La0.7Ba0.3−xKxMnO3 (x = 0 and 0.04) manganites prepared via the solid-state method were investigated.
Abstract: The effects of K+ substitution at the Ba-site on the structural, magnetic, and electrical properties and magnetoresistance (MR) of La0.7Ba0.3−xKxMnO3 (x = 0 and 0.04) manganites prepared via the solid-state method were investigated. Rietveld refinement of X-ray diffraction data confirmed that both samples were crystallized in the rhombohedral structure with the R3c¯ space group. In addition, the unit cell volume, V, and the average grain size also increased with K+ ions. Magnetization versus applied field (M–H) measurement was carried out, and the saturation magnetization (Ms) was found to increase from 1.81 μB/f.u. (x = 0) to 4.11 μB /f.u. (x = 0.04), implying that K+ ions strengthened the ferromagnetic (FM) interaction. Furthermore, the metal–insulator transition temperature, TMI, increased from 257 K (x = 0) to 271 K (x = 0.04). The observed behaviour may be related to the enhancement of double-exchange (DE) interaction due to the increase in Mn-O-Mn bond angle and electronic bandwidth (W), favouring the increasing rate of the eg electron hopping process. The fitting of the electrical resistivity data in the metallic region describes the significance of residual resistivity, electron–electron and electron–magnon scattering processes to elucidate the electronic transport properties. Within the insulating region, variable range hopping (VRH) and small polaron hopping (SPH) models are proposed to describe the conduction mechanism.

Journal ArticleDOI
19 May 2022-Crystals
TL;DR: In this paper , a dc resistivity and magnetization study on manganite La1−xCaxMnO3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and ferromagnetic (FM) metallic phases x=0.5.
Abstract: Among transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)—a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La1−xCaxMnO3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases x=0.5. Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles.

Journal ArticleDOI
TL;DR: Zhang et al. as discussed by the authors reported a noncollinear magnetic structure below the Tc where the moments lie predominantly within the basal plane but tilt toward the c axis by ~10o at ambient conditions.
Abstract: The ferrimagnetic insulator Mn3Si2Te6, which features a Curie temperature Tc at 78 K and a delicate yet consequential magnetic frustration, exhibits colossal magnetoresistance (CMR) when the magnetic field is applied along the magnetic hard axis, surprisingly inconsistent with existing precedents [Y. Ni, H. Zhao, Y. Zhang et al. Phys. Rev. B 103, L161105 (2021)]. This discovery motivates a thorough single-crystal neutron diffraction study in order to gain insights into the magnetic structure and its hidden correlation with the new type of CMR. Here we report a noncollinear magnetic structure below the Tc where the moments lie predominantly within the basal plane but tilt toward the c axis by ~10o at ambient conditions. A substantial magnetic diffuse scattering decays slowly and persists well above the Tc. The evolution of the spin correlation lengths agrees well with the electrical resistivity, underscoring the role of spin fluctuation contributing to the magnetoresistivity near the transition. Application of magnetic field along the c axis, renders a swift occurrence of CMR but only a slow tilting of the magnetic moments toward the c axis. The unparalleled changes indicate a non-consequential role of magnetic polarization.

Journal ArticleDOI
TL;DR: Goodenough as mentioned in this paper discussed the role of mixed valence in transition-metal oxides and their connections to phenomena such as colossal magnetoresistance, enhanced thermopower, and high-temperature superconductivity.
Abstract: In honor of John Goodenough’s centennial birthday, I discuss some of his insights into magnetism and the role of mixed valence in transition-metal oxides. His ideas form an important part of the continuing evolution of our understanding of these fascinating materials with a wide range of technologically-important functionalities. In particular, I will mention connections to phenomena such as colossal magnetoresistance, enhanced thermopower, and high-temperature superconductivity.

Journal ArticleDOI
TL;DR: In this paper , electron spin resonance (ESR) was used to reveal microscopic evidence for the formation of magnetic polarons in antiferromagnetic Eu$5}$In$2}$Sb$6} .
Abstract: Colossal magnetoresistance (CMR) emerges from intertwined spin and charge degrees of freedom in the form of ferromagnetic clusters also known as trapped magnetic polarons. As a result, CMR is rarely observed in antiferromagnetic materials. Here we use electron spin resonance (ESR) to reveal microscopic evidence for the formation of magnetic polarons in antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$. First, we observe a reduction of the Eu$^{2+}$ ESR linewidth as a function of the applied magnetic field consistent with ferromagnetic clusters that are antiferromagnetically coupled. Additionally, the Eu$^{2+}$ lineshape changes markedly below T' ~ 200 K, a temperature scale that coincides with the onset of CMR. The combination of these two effects provide strong evidence that magnetic polarons grow in size below T' and start influencing the macroscopic properties of the system.

Journal ArticleDOI
TL;DR: In this article , the high entropy concept is combined with standard property control by hole doping in a series of single-phase orthorhombic HE•manganites (HE•Mn), (Gd0.25La 0.25Nd 0.1−SrxMnO3 (x = 0.5).
Abstract: Technologically relevant strongly correlated phenomena such as colossal magnetoresistance (CMR) and metal‐insulator transitions (MIT) exhibited by perovskite manganites are driven and enhanced by the coexistence of multiple competing magneto‐electronic phases. Such magneto‐electronic inhomogeneity is governed by the intrinsic lattice‐charge‐spin‐orbital correlations, which, in turn, are conventionally tailored in manganites via chemical substitution, charge doping, or strain engineering. Alternately, the recently discovered high entropy oxides (HEOs), owing to the presence of multiple‐principal cations on a given sub‐lattice, exhibit indications of an inherent magneto‐electronic phase separation encapsulated in a single crystallographic phase. Here, the high entropy (HE) concept is combined with standard property control by hole doping in a series of single‐phase orthorhombic HE‐manganites (HE‐Mn), (Gd0.25La0.25Nd0.25Sm0.25)1‐xSrxMnO3 (x = 0–0.5). High‐resolution transmission microscopy reveals hitherto‐unknown lattice imperfections in HEOs: twins, stacking faults, and missing planes. Magnetometry and electrical measurements infer three distinct ground states—insulating antiferromagnetic, unpercolated metallic ferromagnetic, and long‐range metallic ferromagnetic—coexisting or/and competing as a result of hole doping and multi‐cation complexity. Consequently, CMR ≈1550% stemming from an MIT is observed in polycrystalline pellets, matching the best‐known values for bulk conventional manganites. Hence, this initial case study highlights the potential for a synergetic development of strongly correlated oxides offered by the high entropy design approach.

Journal ArticleDOI
TL;DR: In this article , a low-field magnetoresistance (LFMR) was improved by compounding La0.7Ca 0.3MnO3 with Mn2O3 to create (LCMO)1-x: (Mn2O 3)x (x = 0.16) composites.

Journal ArticleDOI
TL;DR: In this article , the in-plane conductance of graphene partially sandwiched between Ni(111) nanostructures with a width of ∼12.08 Å was analyzed.
Abstract: In this study, we present a theoretical study on the in-plane conductance of graphene partially sandwiched between Ni(111) nanostructures with a width of ∼12.08 Å. In the sandwiched part, the gapped Dirac cone of the graphene was controlled using a pseudospin by changing the magnetic alignment of the Ni(111) nanostructures. Upon considering the antiparallel configuration of Ni(111) nanostructures, the transmission probability calculation of the in-plane conductance of graphene shows a gap-like transmission at E − EF = 0.2 and 0.65 eV from the pd-hybridization and controllable Dirac cone of graphene, respectively. In the parallel configuration, the transmission probability calculation showed a profile similar to that of the pristine graphene. High and colossal magnetoresistance ratios of 284% and 3100% were observed at E − EF = 0.65 eV and 0.2 eV, respectively. Furthermore, a magnetoresistance beyond 3100% was expected at E − EF = 0.65 eV when the width of the Ni(111) nanostructures on the nanometer scale was considered.

Journal ArticleDOI
TL;DR: In this article , an investigation was conducted to understand the electrical behavior of the double-layered perovskite LaCaBiMn2O7 at temperatures varying from 2 to 400 K under a magnetic field range 0-5 T. In order to analyze electrical behavior as well as the magnetic properties, a simulation was established with the resistivity data using a mathematical model based on the percolation theory.

Journal ArticleDOI
TL;DR: In this paper, high-field magnetotransport of KTaO3 single crystals, which are a promising candidate for study in the extreme quantum limit, has been reported, with a significant positive, non-saturating and linear magnetoresistance at low temperatures accompanied by a decreasing Hall coefficient.
Abstract: We report on the high-field magnetotransport of KTaO3 single crystals, which are a promising candidate for study in the extreme quantum limit. By photocarrier doping with 360 nm light, we observe a significant positive, non-saturating, and linear magnetoresistance at low temperatures accompanied by a decreasing Hall coefficient. When cooling down to 10 K, the magnetoresistance value of KTaO3 (100) reaches ∼ 433% at a magnetic field of 12 T. Such behavior can be attributed to all the electrons occupying only the lowest Landau level in the extreme quantum limit. Light inhomogeneity may also contribute to large linear magnetoresistance. These results provide insights into novel magnetic devices based on complex materials and add a new family of materials with positive magnetoresistance.

Journal ArticleDOI
12 Mar 2022
TL;DR: In this article , the ferromagnetic and electrical transport properties of La2/3Sr1/3MnO3 superlattices with artificial A-site cation ordering were investigated.
Abstract: (111)‐oriented [(SrMnO3)1/(LaMnO3)2]n superlattices with artificial A‐site cation ordering with respect to the compositionally equivalent La2/3Sr1/3MnO3 films with a random distribution of the A‐site dopants are fabricated. It is found that the ferromagnetism and electrical transport properties of La2/3Sr1/3MnO3 films are primarily independent of the degree of A‐site cation ordering, as evidenced by their identical critical temperatures of phase transition. These results may reveal the spontaneous nature of the electronic phase separation, which is key to the colossal magnetoresistance effect in manganites. In contrast, compared to the La2/3Sr1/3MnO3 films, the A‐site ordered (111) superlattices have a tendency to preserve oxygen vacancies inside, making them extremely difficult to be compensated by the post‐annealing process.

Journal ArticleDOI
TL;DR: In this article , a massive negative magnetoresistance (CNMR) coexisting with a saturated magnetic moment is reported in the case of Ga1−x Mn x As1−y P y thin films.
Abstract: Ferromagnetic semiconductor Ga1–x Mn x As1–y P y thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers. In this regime, we report a colossal negative magnetoresistance (CNMR) coexisting with a saturated magnetic moment, unlike in the traditional magnetic semiconductor Ga1– x Mn x As. By analyzing the temperature dependence of the resistivity at fixed magnetic field, we demonstrate that the CNMR can be consistently described by the field dependence of the localization length, which relates to a field dependent mobility edge. This dependence is likely due to the random environment of Mn atoms in Ga1–x Mn x As1–y P y which causes a random spatial distribution of the mobility that is suppressed by an increasing magnetic field.

DissertationDOI
21 Feb 2022
TL;DR: In this article , the polaronic behavior at manganite interfaces studied by various Raman spectroscopy techniques was investigated and a strongly Jahn-Teller distorted surface layer of several nanometers thickness was observed.
Abstract: This work focusses on the polaronic behaviour at manganite interfaces studied by various Raman spectroscopy techniques. Temperature- and magnetic-field-dependent studies probe the polaronic behaviour at the internal interfaces within the phase-separated material showing a strong correlation to the metal-insulator transition and colossal magnetoresistance. Surface-Enhanced Raman studies analyze the manganite's surface and show a strongly Jahn-Teller distorted surface layer of several nanometers thickness.

Journal ArticleDOI
TL;DR: The T-dependent Seebeck (S) of several samples belonging to the Sr2Fe1+xRe1-xO6 series (x≤0.33) has been investigated in this article .
Abstract: The T-dependent Seebeck (S) of several samples belonging to the Sr2Fe1+xRe1-xO6 series (x≤0.33) has been investigated. All these polycrystalline samples synthesized by solid state reaction in closed vessels crystallize in the I4/m double perovskite structure. Though ferrimagnetic with TC>400 K, the decrease of their magnetization as x increases from x=0.00 is explained by the cation disorder induced by the deviation from the ideal 1 : 1 Re/Fe ratio for the 2a and 2b crystallographic sites. Interestingly, it is found that at room temperature, the S sign changes from S>0 to S<0 as x increases to about x=0.25. Despite that the magnitude of their magnetoresistance, near −20 % in 9T and at T=5 K, is not very sensitive to x, a positive magneto Seebeck effect is observed only for the samples exhibiting S(300 K)>0. This asymmetry in the magnetothermopower properties of the n- and p-type samples is interpreted in the framework of the spin polarized transport of these magnetoresistive double-perovskites.


Posted ContentDOI
14 Oct 2022
TL;DR: In this article , a large linear positive magnetoresistance (LMR) was reported in LaTiO3/SrTiO 3 heterostructures, with LMR amplitude reaching up to 6500% at 9T. This was explained by the unusual combination of a very high thin film mobility, up to 40 000 cm$^2$/V.s, and a very large coverage of low-mobility regions.
Abstract: Linear magnetoresistance (LMR) is of particular interest for memory, electronics, and sensing applications, especially when it does not saturate over a wide range of magnetic fields. One of its principal origins is local mobility or density inhomogeneities, often structural, which in the Parish-Littlewood theory leads to an unsaturating LMR proportional to mobility. Structural disorder, however, also tends to limit the mobility and hence the overall LMR amplitude. An alternative route to achieve large LMR is via non-structural inhomogeneities which do not affect the zero field mobility, like magnetic domains. Here, linear positive magnetoresistance caused by magnetic texture is reported in \ch{LaTiO3}/\ch{SrTiO3} heterostructures. The LMR amplitude reaches up to 6500\% at 9T. This colossal value is understood by the unusual combination of a very high thin film mobility, up to 40 000 cm$^2$/V.s, and a very large coverage of low-mobility regions. These regions correlate with a striped magnetic structure, compatible with a spiral magnetic texture in the \ch{LaTiO3} film, revealed by low temperature Lorentz transmission electron microscopy. These results provide a novel route for the engineering of large-LMR devices.

Book ChapterDOI
01 Jan 2022
TL;DR: In this paper, an atomistic computational analysis was performed for LSMO using quantum ATK and the effective mass [m*(me)] was calculated as 0.025 and −0.539 at 671 band index (−0.134 eV energy) and 672 band index (0.124 energy) respectively.
Abstract: Colossal magnetoresistance (CMR) was observed in a few ferromagnetic materials (FM) such as La0.71Sr0.29MnO3 (LSMO). LSMO bearing greater magnetoresistance effect has the potential application in high-density information storage, spin valve and sensor technology. The atomistic computational analysis was performed for LSMO using quantum ATK. From LSMO bandstructure plots bandgap was observed at 0 eV bandgap at Ef (Fermi level). Overlap bandstructure predicted its ferromagnetic property. Effective mass [m*(me)] was calculated as 0.025 and −0.539 at 671 band index (−0.134 eV energy) and 672 band index (−0.124 eV energy). DOS plots of LSMO show a higher number of states at the Fermi level (by observing the number of spikes), depicting its application as a high-density device. The highest peak at the valance band was observed at −18 eV energy. p and d orbitals contributed to a larger number of states in DOS plots. Computation of transmission spectrum helped in predicting TMR by providing conductance value of the material used. Mulliken population observation leads to the prediction of atomic conjunction in the material. Thus, the electrical and electronic properties depicted superior properties of LSMO as FM. Implementing LSMO-based ferromagnetic layers in MTJ memory device is of high interest.


Journal ArticleDOI
TL;DR: In this paper , Nd-Ca-based manganite Nd0.5Ca 0.5Ti0.1Mn0.9O3 and 10% Ti-doped manganitic Nd 0.1mn 0.6O3 were prepared using solid state reaction method.
Abstract: Nd-Ca-based manganite Nd0.5Ca0.5MnO3 and 10% Ti-doped manganite Nd0.5Ca0.5Ti0.1Mn0.9O3 denoted by N and N0.1, respectively, were prepared using solid-state reaction method. Resistivity gets increased for the Ti-doped sample. The parent compound N has remarkably high magnetoresistance. The highest value of Seebeck coefficient for N is -97 μVK-1 at 143 K and for N0.1 is -207 μVK-1 at 203 K. Variable range hopping mechanism successfully explains the high temperature resistivity and thermopower data. Keywords: magnetoresistance, thermoelectric power, rare-earth based manganites, manganites.