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Showing papers on "Magnetoresistance published in 1999"


Journal ArticleDOI
TL;DR: A review of the literature on mixed-valence manganites, placing new results in the context of established knowledge of these materials, and other magnetic semiconductors, is given in this paper.
Abstract: Mixed-valence manganese oxides (R1-χAχ)MnO3 (R=rare-earth cation, A=alkali or alkaline earth cation), with a structure similar to that of perovskite CaTiO3, exhibit a rich variety of crystallographic, electronic and magnetic phases. Historically they led to the formulation of new physical concepts such as double exchange and the Jahn-Teller polaron. More recent work on thin films has revealed new phenomena, including colossal magnetoresistance near the Curie temperature, dense granular magnetoresistance and optically-induced magnetic phase transitions. This review gives an account of the literature on mixed-valence manganites, placing new results in the context of established knowledge of these materials, and other magnetic semiconductors. Issues addressed include the nature of the electronic ground states, the metal-insulator transition as a function of temperature, pressure and applied magnetic field, the electronic transport mechanisms, dielectric and magnetic polaron formation, magnetic localization, ...

1,757 citations


Journal ArticleDOI
16 Dec 1999-Nature
TL;DR: In this article, the magnetic semiconductor BexMnyZn1-x-ySe is used as a spin aligner to inject spin-polarized charge into a non-magnetic semiconductor device.
Abstract: The field of magnetoelectronics has been growing in practical importance in recent years1 For example, devices that harness electronic spin—such as giant-magnetoresistive sensors and magnetoresistive memory cells—are now appearing on the market2 In contrast, magnetoelectronic devices based on spin-polarized transport in semiconductors are at a much earlier stage of development, largely because of the lack of an efficient means of injecting spin-polarized charge Much work has focused on the use of ferromagnetic metallic contacts3,4, but it has proved exceedingly difficult to demonstrate polarized spin injection More recently, two groups5,6 have reported successful spin injection from an NiFe contact, but the observed effects of the spin-polarized transport were quite small (resistance changes of less than 1%) Here we describe a different approach, in which the magnetic semiconductor BexMnyZn1-x-ySe is used as a spin aligner We achieve injection efficiencies of 90% spin-polarized current into a non-magnetic semiconductor device The device used in this case is a GaAs/AlGaAs light-emitting diode, and spin polarization is confirmed by the circular polarization state of the emitted light

1,650 citations


Journal ArticleDOI
10 Jun 1999-Nature
TL;DR: In this article, it was shown that the magnetoresistive response increases dramatically when the Curie temperature (T C) is reduced, and that the massive magnetoresistance in low-T C systems can be explained by percolative transport through the ferromagnetic domains; this depends sensitively on the relative spin orientation of adjacent magnetoric domains which can be controlled by applied magnetic fields.
Abstract: Colossal magnetoresistance1—an unusually large change of resistivity observed in certain materials following application of magnetic field—has been extensively researched in ferromagnetic perovskite manganites. But it remains unclear why the magnetoresistive response increases dramatically when the Curie temperature (T C) is reduced. In these materials, T C varies sensitively with changing chemical pressure; this can be achieved by introducing trivalent rare-earth ions of differing size into the perovskite structure2,3,4, without affecting the valency of the Mn ions. The chemical pressure modifies local structural parameters such as the Mn–O bond distance and Mn–O–Mn bond angle, which directly influence the case of electron hopping between Mn ions (that is, the electronic bandwidth). But these effects cannot satisfactorily explain the dependence of magnetoresistance on T C. Here we demonstrate, using electron microscopy data, that the prototypical (La,Pr,Ca)MnO3 system is electronically phase-separated into a sub-micrometre-scale mixture of insulating regions (with a particular type of charge-ordering) and metallic, ferromagnetic domains. We find that the colossal magnetoresistive effect in low-T C systems can be explained by percolative transport through the ferromagnetic domains; this depends sensitively on the relative spin orientation of adjacent ferromagnetic domains which can be controlled by applied magnetic fields.

1,417 citations


Journal ArticleDOI
06 Aug 1999-Science
TL;DR: Current-induced switching in the orientation of magnetic moments is observed in cobalt/copper/cobalt sandwich structures, for currents flowing perpendicularly through the layers, in accord with predictions that a spin-polarized current exerts a torque at the interface between a magnetic and nonmagnetic metal.
Abstract: Current-induced switching in the orientation of magnetic moments is observed in cobalt/copper/cobalt sandwich structures, for currents flowing perpendicularly through the layers. Magnetic domains in adjacent cobalt layers can be manipulated controllably between stable parallel and antiparallel configurations by applying current pulses of the appropriate sign. The observations are in accord with predictions that a spin-polarized current exerts a torque at the interface between a magnetic and nonmagnetic metal, due to local exchange interactions between conduction electrons and the magnetic moments.

1,247 citations


Journal ArticleDOI
TL;DR: In this paper, exchange biased magnetic tunnel junction (MTJ) structures are shown to have useful properties for forming magnetic memory storage elements in a novel cross-point architecture, which exhibit very large magnetoresistive (MR) values exceeding 40% at room temperature, with specific resistance values ranging down to as little as ∼60 Ω(μm)2.
Abstract: Exchange biased magnetic tunnel junction (MTJ) structures are shown to have useful properties for forming magnetic memory storage elements in a novel cross-point architecture. MTJ elements have been developed which exhibit very large magnetoresistive (MR) values exceeding 40% at room temperature, with specific resistance values ranging down to as little as ∼60 Ω(μm)2, and with MR values enhanced by moderate thermal treatments. Large MR values are observed in magnetic elements with areas as small as 0.17 (μm)2. The magnetic field dependent current–voltage characteristics of an MTJ element integrated with a silicon diode are analyzed to extract the MR properties of the MTJ element itself.

1,110 citations


Journal ArticleDOI
TL;DR: In this article, the experimental and theoretical results on III-V-based ferromagnetic semiconductors ((In,Mn)As and (Ga, Mn)As) accumulated to date.

728 citations


Journal ArticleDOI
07 Oct 1999-Nature
TL;DR: In this article, the authors reported the injection of spin-polarized electrons from ferromagnetic contacts into multi-walled carbon nanotubes, finding direct evidence for coherent transport of electron spins.
Abstract: Conventional electronic devices generally utilize only the charge of conduction electrons; however, interest is growing in ‘spin-electronic’ devices1, whose operation depends additionally on the electronic spin. Spin-polarized electrons (which occur naturally in ferromagnetic materials) can be injected from a ferromagnet into non-ferromagnetic materials2,3,4, or through oxide tunnel barriers3,5,6,7,8,9,10. The electron-scattering rate at any subsequent ferromagnetic/non-ferromagnetic interface depends on the spin polarity, a property that is exploited in spin-electronic devices. The unusual conducting properties11,12,13,14,15,16,17,18 of carbon nanotubes offer intriguing possibilities for such devices; their elastic- and phase-scattering lengths are extremely long16,17, and carbon nanotubes can behave as one-dimensional conductors18. Here we report the injection of spin-polarized electrons from ferromagnetic contacts into multi-walled carbon nanotubes, finding direct evidence for coherent transport of electron spins. We observe a hysteretic magnetoresistance in several nanotubes with a maximum resistance change of 9%, from which we estimate the spin-flip scattering length to be at least 130 nm—an encouraging result for the development of practical nanotube spin-electronic devices.

692 citations


Journal ArticleDOI
TL;DR: In this article, the lattice constants of both a and c axes of wurtzite Zn1−xMnxO films (x < 0.35) increase and the band gap expands although considerable in-gap absorption develops.
Abstract: Epitaxial thin films of an oxide-diluted magnetic semiconductor, Mn-doped ZnO, were fabricated by pulsed-laser deposition technique. Solubility of Mn into ZnO exceeds thermal equilibrium limit as a result of nonequilibrium film growth process. As Mn content is increased, the lattice constants of both a and c axes of wurtzite Zn1−xMnxO films (x<0.35) increase and the band gap expands although considerable in-gap absorption develops. Itinerant electrons over 1019 cm−3 can be doped into the Zn1−xMnxO films by Al doping, in contrast to low carrier density in the other II–VI diluted magnetic semiconductors. The temperature dependence of the resistivity is almost metallic and considerable magnetoresistance is observed at low temperatures.

657 citations


Journal ArticleDOI
25 Feb 1999-Nature
TL;DR: In this paper, the authors reported magnetoresistance measurements on individual multi-walled carbon nanotubes and found that the oscillations are in good agreement with theoretical predictions for the Aharonov-Bohm effect in a hollow conductor with a diameter equal to that of the outermost shell of the nanotube.
Abstract: When electrons pass through a cylindrical electrical conductor aligned in a magnetic field, their wave-like nature manifests itself as a periodic oscillation in the electrical resistance as a function of the enclosed magnetic flux1. This phenomenon reflects the dependence of the phase of the electron wave on the magnetic field, known as the Aharonov–Bohm effect2, which causes a phase difference, and hence interference, between partial waves encircling the conductor in opposite directions. Such oscillations have been observed in micrometre-sized thin-walled metallic cylinders3,4,5 and lithographically fabricated rings6,7,8. Carbon nanotubes9,10 are composed of individual graphene sheets rolled into seamless hollow cylinders with diameters ranging from 1 nm to about 20 nm. They are able to act as conducting molecular wires11,12,13,14,15,16,17,18, making them ideally suited for the investigation of quantum interference at the single-molecule level caused by the Aharonov–Bohm effect. Here we report magnetoresistance measurements on individual multi-walled nanotubes, which display pronounced resistance oscillations as a function of magnetic flux.We find that the oscillations are in good agreement with theoretical predictions for the Aharonov–Bohm effect in a hollow conductor with a diameter equal to that of the outermost shell of the nanotubes. In some nanotubes we also observe shorter-period oscillations, which might result from anisotropic electron currents caused by defects in the nanotube lattice.

656 citations


Journal ArticleDOI
03 Sep 1999-Science
TL;DR: The results suggest that the transition and the associated magnetoresistance behavior should be viewed as a percolation of metallic ferromagnetic domains.
Abstract: Scanning tunneling spectroscopy was used to investigate single crystals and thin films of La1– x Ca x MnO3(with x of about 0.3), which exhibit colossal magnetoresistance. The different spectroscopic signatures of the insulating (paramagnetic) and metallic (ferromagnetic) phases enable their spatial extent to be imaged down to a lateral scale of the order of 10 nanometers. Above the bulk transition temperature T c, the images show mostly insulating behavior. Below T c, a phase separation is observed where inhomogeneous structures of metallic and more insulating areas coexist and are strongly field dependent in their size and structure. Insulating areas are found to persist far below T c. These results suggest that the transition and the associated magnetoresistance behavior should be viewed as a percolation of metallic ferromagnetic domains.

650 citations


Journal ArticleDOI
15 Oct 1999-Science
TL;DR: The role of the metal-oxide interface in determining the spin polarization of electrons tunneling from or into ferromagnetic transition metals in magnetic tunnel junctions is reported and the results are ascribed to bonding effects at the transition metal-barrier interface.
Abstract: The role of the metal-oxide interface in determining the spin polarization of electrons tunneling from or into ferromagnetic transition metals in magnetic tunnel junctions is reported. The spin polarization of cobalt in tunnel junctions with an alumina barrier is positive, but it is negative when the barrier is strontium titanate or cerium lanthanite. The results are ascribed to bonding effects at the transition metal-barrier interface. The influence of the electronic structure of metal-oxide interfaces on the spin polarization raises interesting fundamental problems and opens new ways to optimize the magnetoresistance of tunnel junctions.

Journal ArticleDOI
21 May 1999-Science
TL;DR: Single-crystal bismuth thin films 1 to 20 micrometers thick were fabricated by electrodeposition and suitable annealing, and clean Shubnikov-de Haas oscillations were observed, indicative of the high quality of these films.
Abstract: Single-crystal bismuth thin films 1 to 20 micrometers thick were fabricated by electrodeposition and suitable annealing. Magnetoresistance up to 250 percent at 300 kelvin and 380,000 percent at 5 kelvin as well as clean Shubnikov-de Haas oscillations were observed, indicative of the high quality of these films. A hybrid structure was also made that showed a large magnetoresistive effect of 30 percent at 200 oersted and a field sensitivity of 0.2 percent magnetoresistance per oersted at room temperature.

Journal ArticleDOI
18 May 1999
TL;DR: Progress on improving the material structures, memory bits, thermal stability of the bits, and competitive architectures for GMR and MTJ based MRAM memories as well as the potential of these memories in the commercial memory market are discussed.
Abstract: We summarize the features of existing semiconductor memories and compare them to Magnetoresistive Random Access Memory (MRAM),a semiconductor memory with magnetic bits for nonvolatile storage. MRAM architectures based on Giant Magnetoresistance (GMR) and Magnetic Tunnel Junction (MTJ) cells are described. This paper will discuss our progress on improving the material structures, memory bits, thermal stability of the bits, and competitive architectures for GMR and MTJ based MRAM memories as well as the potential of these memories in the commercial memory market.

Journal ArticleDOI
TL;DR: In this article, the first-principles band calculation predicts that the half metallic ground state with the ferrimagnetic coupling of Fe and Re spins has been obtained and the experimental results of electronic and magnetic properties are in accord with this picture.
Abstract: Intergrain tunneling magnetoresistance (TMR) subsisting up to room temperature has been observed for polycrystalline ceramics of ${\mathrm{Sr}}_{2}{\mathrm{FeReO}}_{6},$ which has ordered double perovskite structure with Curie temperature above 400 K. The first-principles band calculation predicts that ${\mathrm{Sr}}_{2}{\mathrm{FeReO}}_{6}$ shows the half metallic ground state with the ferrimagnetic coupling of Fe and Re spins. The experimental results of electronic and magnetic properties are in accord with this picture. In fact, the magnitude of intergrain TMR with the magnetic field of 7 T at 4.2 and 300 K is as large as 21 and 7%, respectively, reflecting high spin polarization of carriers.

Journal ArticleDOI
TL;DR: In this article, an experimentalist's view of the theory and published data for the magnetoresistance (MR) of a multilayer composed of alternating ferromagnetic (F) and non-magnetic (N) metals measured with current flow perpendicular to the layer planes (CPP-MR) is presented.

Journal ArticleDOI
TL;DR: In this paper, magnetoresistance experiments in magnetic Ni nanocontacts in the ballistic transport regime at room temperature were conducted and it was shown that the magnetoreduction for a few-atom contact reaches values of $280%$ at room-temperature and for applied magnetic fields of 100 Oe.
Abstract: We present magnetoresistance experiments in magnetic Ni nanocontacts in the ballistic transport regime at room temperature. It is shown that the magnetoresistance for a few-atom contact reaches values of $280%$ at room temperature and for applied magnetic fields of 100 Oe. Results are presented for over 50 samples showing the trend that the smaller the contact the larger the magnetoresistance response. This indicates that the effect arises just at the nanocontact.

Journal ArticleDOI
TL;DR: In this paper, a surface and/or interface related dead layer is inferred from the thickness-dependent resistance and magnetoresistance of ultrathin films of La0.67Sr0.33MnO3.
Abstract: To understand the near-interface magnetism in manganites, ultrathin films of La0.67Sr0.33MnO3 were grown epitaxially on single-crystal (001) LaAlO3 and (110) NdGaO3 substrates. The temperature and magnetic field-dependent film resistance is used to probe the film’s structural and magnetic properties. A surface and/or interface related dead layer is inferred from the thickness-dependent resistance and magnetoresistance. The total thickness of the dead layer is estimated to be ∼30 A for films on NdGaO3 and ∼50 A for films on LaAlO3.

Journal ArticleDOI
Patrick Bruno1
TL;DR: In this article, the structure and properties of a geometrically constrained magnetic wall in a constriction separating two wider regions are investigated theoretically, and it is shown that these properties are differconsiderably from those of an unconstrained wall.
Abstract: The structure and properties of a geometrically constrained magnetic wall in a constriction separating two wider regions are investigated theoretically. They are shown to differconsiderably from those of an unconstrained wall, so that the geometrically constrained magnetic wall truly constitutes a new kind of magnetic wall, besides the well known Bloch and Neel walls. In particular, the width of a constrained wall cann become very small if the characteristic length of the constriction is small, as is actually the case in an atomic point contact. This provides a simple, natural explanation for the large magnetoresistance observed in ferromagnetic atomic point contacts.

Journal ArticleDOI
TL;DR: In this paper, the phase-coherence and elastic-scattering lengths of single-wall nanotubes were deduced based on Fermi-liquid and Luttinger-liquid theory.
Abstract: We report equilibrium electric resistance R and tunneling spectroscopy (dI/dV)measurements obtained on single multi-wall nanotubes contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance. The phase-coherence (lφ)and elastic-scattering lengths (le)are deduced. Because le is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum which is in good agreement with the density of states (DOS) due to the one-dimensional subbands expected for a perfect single-wall tube. As a function of temperature T the resistance increases on decreasing T and saturates at ≈1–10 Kfor all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small voltage scale of the order ≈10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-liquid theories for nanotubes. Because we have used quantum diffusion based on Fermi-liquid as well as Luttinger-liquid theory in trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.

Journal ArticleDOI
Ayush Gupta1, Jonathan Z. Sun1
TL;DR: In this paper, the authors showed that the magnetic oxide materials possessing a high degree of spin polarization exhibit enhanced spin-dependent transport properties at low-fraction-of-power conditions.

Journal ArticleDOI
TL;DR: In this article, the authors reviewed the experimental results and the current theoretical understanding of FM-I-FM tunneling and its dependence on bias, temperature, and barrier characteristics, and the influence of inelastic tunneling processes and material properties on the junction magnetoresistance.
Abstract: ▪ Abstract Based on the spin conservation in electron tunneling across an insulator (I) and the spin polarization of conduction electrons in ferromagnets (FM) established by Meservey and Tedrow, Julliere put forward a quantitative model (1975) showing that tunneling in FM-I-FM junctions should lead to a large junction magnetoresistance (JMR). This conjecture was realized with repeatable results only in 1995, and since then JMR values >30% have been achieved at room temperature. This phenomenon has tremendous potential for applications as nonvolatile magnetic memory elements, read heads, and picotesla field sensors. We review the experimental results and the current theoretical understanding of FM-I-FM tunneling and its dependence on bias, temperature, and barrier characteristics. The influence of inelastic tunneling processes and material properties on the JMR is extensively discussed. Early theories are reviewed and their relationship to the linear response theory is presented. Future directions, both fr...

Journal ArticleDOI
TL;DR: The magnetoresistance of La2/3Sr1/3MnO3/CeO2 composites is explored as a function of the metal/insulator composition, temperature, and magnetic field as mentioned in this paper.
Abstract: The magnetoresistance of La2/3Sr1/3MnO3/CeO2 composites is explored as a function of the metal/insulator composition, temperature, and magnetic field. An important enhancement of the low-field magnetoresistance is observed for samples close to metallic percolation threshold. The improved field sensitivity is still fairly large at room temperature. Manganese perovskites composites may constitute a new alternative for the development of magnetoresistive devices.

Journal ArticleDOI
TL;DR: In this article, the full magnetoresistive hysteresis loops of single Ni and Co nanowires, including the irreversible jump, are understood qualitatively, and major progress has been made towards their quantitative description, on the basis of anisotropic magnetoresistance.
Abstract: Magnetoresistance of single Ni and Co nanowires, of about 60 nm in diameter and 6000 nm in length, was measured at room temperature. The full magnetoresistive hysteresis loops of single Ni nanowires, including the irreversible jump, are understood qualitatively, and major progress has been made towards their quantitative description, on the basis of anisotropic magnetoresistance. In contrast, the magnetoresistive hysteresis loops of single Co nanowires could not be described quantitatively, due to the presence of nucleation processes of domain walls or vortices.

Journal ArticleDOI
TL;DR: In this paper, the phase-coherence and elastic-scattering lengths of single-wall nanotubes were deduced based on Luttinger-Liquid theory, and a large fraction of the paper is devoted to a careful discussion of all the results.
Abstract: We report equilibrium electric resistance R and tunneling spectroscopy dI/dV measurements obtained on single multiwall nanotubes contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance. The phase-coherence and elastic-scattering lengths are deduced. Because the latter is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum which is in good agreement with the density-of-states (DOS) due to the one-dimensional subbands expected for a perfect single-wall tube. As a function of temperature T the resistance increases on decreasing T and saturates at approx. 1-10 K for all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small voltage scale of order 10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-Liquid theories for nanotubes. Because we have used quantum diffusion based on Fermi-Liquid as well as Luttinger-Liquid theory in trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.

Journal ArticleDOI
TL;DR: In this paper, a mean-field theory of carrier-induced ferromagnetic magnetoreduction in diluted magnetic semiconductors has been developed, which is an improvement over the standard Ruderman-Kittel-Kesuya-Yosida model allowing spatial inhomogeneity of the system, free-carrier spin polarization, finite temperature, and freecarrier exchange and correlation to be accounted for selfconsistently.
Abstract: We develop a mean-field theory of carrier-induced ferromagnetism in diluted magnetic semiconductors. Our approach represents an improvement over standard Ruderman-Kittel-Kesuya-Yosida model allowing spatial inhomogeneity of the system, free-carrier spin polarization, finite temperature, and free-carrier exchange and correlation to be accounted for self-consistently. As an example, we calculate the electronic structure of a ${\mathrm{Mn}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}$As/GaAs superlattice with alternating ferromagnetic and paramagnetic layers and demonstrate the possibility of semiconductor magnetoresistance systems with designed properties.

Journal ArticleDOI
18 May 1999
TL;DR: In this paper, highfrequency noise suppressors or anti-reflection absorbers were proposed for use with M-hexaferrites with planar magnetic anisotropy, which leads to higher magnetic resonance frequency, and thus a large absorption loss in sintered specimens and small reflection loss (in rubber composites) are predicted at the higher frequencies in the substituted specimens.
Abstract: Magnetic and microwave absorbing properties have been investigated in the M-type barium ferrites (BaFe/sub 12-2x/A/sub x/Co/sub x/O/sub 19/) with planar magnetic anisotropy. For the tetravalent A ions, Ti/sup 4+/ and Ru/sup 4+/ are chosen and the samples are prepared by a conventional ceramic processing technique. At the substitution ratio with in-plane anisotropy which is estimated from the minimum coercivity, the saturation magnetization of the Ru-Co substituted specimens were about twice as large as those of Ti-Co. This leads to higher magnetic resonance frequency, and thus a large absorption loss (in sintered specimens) and small reflection loss (in rubber composites) are predicted at the higher frequencies in the Ru-Co substituted specimens. High-frequency noise suppressors or anti-reflection absorbers can be proposed for use with M-hexaferrites with planar magnetic anisotropy.

Journal ArticleDOI
TL;DR: In this article, the authors reported significant enhancements of magnetoresistance in granular (La0.67Ca0.33MnO3)x/(SrTiO31−x) systems with high (around 5 T) and low (a few hundred Oersted) fields.
Abstract: We report significant enhancements of magnetoresistance in granular (La0.67Ca0.33MnO3)x/(SrTiO3)1−x. The system exhibits a conduction threshold at x=xc∼60%, around which magnetoresistance versus x has a maximum. The composition xc at which maximum enhancement in magnetoresistance is observed is the same at high (around 5 T) and at low (a few hundred Oersted) fields. The enhancement is consistent with the disorder-driven amplification of spin-dependent transport at the structural boundaries of the mixture.

Journal ArticleDOI
TL;DR: In this article, the authors reported significant intergrain magnetoresistance (IMR) in polycrystalline double perovskites of SrFe1−x(Mo1/2O3) at room temperature, indicating that a new avenue for spin-polarized tunneling junctions is to utilize insulating interface layers with ferromagnetic or ferrimagnetic coupling.
Abstract: We report significant intergrain magnetoresistance (IMR) in polycrystalline double perovskites of SrFe1−x(Mo or Re)xO3 at room temperature. Systematics of the temperature dependence of IMR indicates that the observed large room-temperature IMR in SrFe1/2Mo1/2O3 originates from the ferrimagnetic nature of insulating grain boundaries as well as the half-metallicity of this perovskite. Our results indicate that a new avenue for spin-polarized tunneling junctions is to utilize insulating interface layers with ferromagnetic or ferrimagnetic coupling.

Journal ArticleDOI
TL;DR: In this article, the authors present theory and experiments in good agreement for ballistic magnetoresistance in nanoscopic-size contacts in 3 $d$ metals (Ni and Co) and find that values of the ballistic magnetoconductance of $\ensuremath{\sim}300%$ at room temperature can be explained by the domain wall which is trapped in the constriction region.
Abstract: We present theory and experiments in good agreement for ballistic magnetoresistance in nanoscopic-size contacts in 3 $d$ metals (Ni and Co) It is found that values of the ballistic magnetoconductance of $\ensuremath{\sim}300%$ at room temperature can be explained by scattering by the domain wall which is trapped in the constriction region These values are obtained for very small contacts and they decrease very fast as the contact size increases The theory also explains this behavior

Journal ArticleDOI
TL;DR: In this paper, the existence of a ferrimagnetic state at low temperatures has been shown to be disproved by electron spin-down t 2g electrons using magnetic and structural characterisation.