Showing papers on "Colossal magnetoresistance published in 1993"
TL;DR: The samples show a drop in the resistivity at the magnetic transition, and the existence of magnetic polarons seems to dominate the electric transport in this region.
Abstract: At room temperature a large magnetoresistance, \ensuremath{\Delta}R/R(H=0), of 60% has been observed in thin magnetic films of perovskitelike La-Ba-Mn-O. The films were grown epitaxially on ${\mathrm{SrTiO}}_{3}$ substrates by off-axis laser deposition. In the as-deposited state, the Curie temperature and the saturation magnetization were considerably lower compared to bulk samples, but were increased by a subsequent heat treatment. The samples show a drop in the resistivity at the magnetic transition, and the existence of magnetic polarons seems to dominate the electric transport in this region.
3,424 citations
TL;DR: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure as mentioned in this paper.
Abstract: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.
995 citations
16 Mar 1993
TL;DR: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure as discussed by the authors.
Abstract: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.
924 citations
TL;DR: In this paper, an effect of the Fermi velocity on the magnetoresistance of Fe/Cr multilayers is examined based on a local-density electronic structure calculation, which is remarkably enhanced by a change in the magnetic alignment of adjacent Fe layers from anti-parallel to parallel.
28 citations
TL;DR: In this article, the microscopic origin of the giant magnetoresistance in metallic multilayers is ascribed to a spin dependent random exchange potential caused by roughness of the interfaces.
18 citations
TL;DR: The magnetoresistance results on the superconducting side of the transition suggest that the insulator-superconductor transition in quench-condensed granular Pb films is directly probing the finite length scales associated with the range of phase coherence in these granular materials.
Abstract: We have studied the insulator-superconductor transition in quench-condensed granular Pb films from 0.1 to 10 K. Resistance measurements were made in zero magnetic field and low noise conditions. Magnetoresistance measurements were also performed for low magnetic fields (less than 100 G). The magnetoresistance results on the superconducting side of the transition suggest that we are directly probing the finite length scales associated with the range of phase coherence in these granular materials.
15 citations
TL;DR: In this article, the authors reported the observation of a previously unobserved positive magnetoresistance effect in several antiferromagnetic-coupled magnetic multilayers, which is a consequence of Lorentz magnetoreduction.
Abstract: We report the observation of a previously unobserved positive magnetoresistance effect in several antiferromagnetically coupled magnetic multilayers. The effect is typically very small with the largest magnetoresistance values observed of less than 0.1% at 4.2 K. We find that the effect is common in magnetic multilayers comprised of magnetic layers of Fe and Co and spacer layers composed of elements from the left hand portions of the 4d and 5d transition metal periods. We propose the magnetoresistance is a consequence of Lorentz magnetoresistance and is unrelated to the giant magnetoresistance effect observed in related structures.
14 citations
TL;DR: In this article, the magnetoresistance of Co Ru epitaxial superlattices with either perpendicular or in-plane magnetisation was studied and an oscillatory behavior of the saturation field and magnetoresphere as a function of Ru layer thickness was found.
9 citations
TL;DR: The magnetoresistance was measured for both H∥c-axis and H⊥;c -axis, using c-axis oriented films with x≥0.6 and 0.7 in the Y1−xPrxBa2Cu3Oy system as discussed by the authors.
Abstract: The magnetoresistance was measured for both H∥c-axis and H⊥;c-axis, using c-axis oriented films with x≥0.6 of the Y1−xPrxBa2Cu3Oy system. The sheet resistance for the CuO2 layer of the sample with x=0.6 is in agreement with h 4e 2 =6400 Ω □ which is the threshold value of a superconducting-insulator (SI) transition in the two-dimensional system. Furthermore, in the samples with x=0.6 and 0.7 a negative magnetoresistance was observed in a wide temperature range below 50 K. Its magnitude is much larger for H∥c-axis than for H ⊥;c-axis. The origin of the negative magnetoresistance is interpreted as a localization effect because those samples have the Pr concentration around the SI transition in the present system. It is pointed out that the disappearance of the superconductivity at xcr∼0.55 originates from the localization effect by Pr doping.
8 citations
TL;DR: The negative magnetoresistance was observed in flux-grown single crystal Y 0.70 Pr 0.30 Ba 2 Cu 3 O 7−y with magnetic field applied either perpendicular or parallel to the ab plane up to 15T as mentioned in this paper.
8 citations
TL;DR: In this paper, the magnetic anisotropic magnetoresistance effect of alloy and superlattice multilayer films has been investigated and the usefulness for phenomenological explanation of both the anisotropesistance and giant magnetoresis of the two-current model, suggested first by Motto and subsequently extended by several researchers, is stressed.
Abstract: The anisotropic magnetoresistance effect of alloy films and so-called giant magnetoresistance of superlattice multilayer films are reviewed. The usefulness for phenomenological explanation of both the anisotropic magnetoresistance and giant magnetoresistance of the two-current model, suggested first by Motto and subsequently extended by several researchers, is stressed. The relationship between the magnetoresistance and the magnetic anisotropy field is demonstrated for films exhibiting either anisotropic magnetoresistance or giant magnetoresistance. The magnetoresistances of multilayer films both with and without magnetic interaction between adjacent layers are compared. The dependence of the magnetoresistance on temperature is briefly discussed.
Journal Article•
13 Apr 1993
01 Jan 1993
TL;DR: In this article, it was found that the magnetic atoms are exchange-coupled via a spin polarization of the conduction electrons of the host metal, which is of the well-known Ruderman-Kittel-Kasuya-Yosida (RKKY) form.
Abstract: The indirect magnetic exchange coupling of magnetic moments via non-magnetic metals has attracted considerable interest over the past few decades. Much work has been carried out on systems comprised of low concentrations of magnetic atoms randomly distributed in metallic hosts, for example, Mn or Fe atoms dissolved in Cu or Au. It was found that the magnetic atoms are exchange-coupled via a spin polarization of the conduction electrons of the host metal1-3. The spin polarization has been inferred from, for example, Cu63 nuclear magnetic resonance (NMR) measurements in which satellites are observed surrounding the main NMR line3. The satellites, corresponding to successive spherical shells of Cu atoms surrounding the magnetic impurities, are shifted alternately to higher and lower magnetic resonance fields resulting from oscillations in the spin polarization of the Cu conduction electrons. For higher concentrations of magnetic impurities the oscillating spin polarization is manifested as an oscillating exchange interaction, alternating between ferromagnetic and antiferromagnetic coupling depending on the separation of the magnetic impurities. This coupling is of the well-known Ruderman-Kittel-Kasuya-Yosida (RKKY) form (see, for example,4).
Journal Article•
TL;DR: In this article, the theory of the giant magnetoresistance effect in multilayer films has been investigated, placing emphasis on its mechanism and dependence on the constituent materials of multilayers.
Abstract: Recently it has been found that metallic multilayer films exhibit novel phenomena, particularly giant magnetoresistance in Fe/Cr, Co/Cu, Co/Cu/NiFe/Cu, and other multilayers. In this review, we explicate the theory of the giant magnetoresistance effect, placing emphasis on its mechanism and dependence on the constituent materials of multilayers. Some relations between the giant magnetoresistance, the electrical resistivity of the magnetic alloys, and the anisotropic magnetoresistance are also discussed.
TL;DR: In this paper, the authors investigated the resistive transition of bulk YBCO samples in low d.c. magnetic fields and found that the under-field resistance becomes notably higher than the resistance prior to field application.
Abstract: The nature of the resistive transition of bulk YBCO samples in low d.c. magnetic fields was investigated. Just below the phase transition onset, the under-field resistance becomes notably higher than the resistance prior to field application. In addition a difference between the resistance after field removal and the resistance prior to its application is also observed. Over part of the temperature range, this resistance exhibits anomalous negative remanent magnetoresistance. A qualitative interpretation is proposed.
13 Apr 1993