Mechanism Of Giant Magnetoresistance Research Articles

Magnetoresistance of lanthanum manganites with activation-type conductivity

The temperature dependence of the resistivity and magnetic moment of La0.85Ba0.15MnO3 and La0.85Sr0.15MnO3 manganite single crystals in magnetic fields up to 90 kOe is investigated. Analysis of the experimental results shows that the magnetoresistance of lanthanum manganites far from the Curie temperature TC can be described quantitatively by the s-d model normally used for ferromagnets and taking into account only the exchange interaction between the spins of charge carriers and magnetic moments. These data also show that the features of lanthanum manganites responsible for colossal magnetoresistance (CMR) are manifested in a narrow temperature interval δT ≈ 20 K near TC. Our results suggest a CMR mechanism analogous to the mechanism of giant magnetoresistance (GMR) observed in Fe/Cr-type multilayers with nanometer layer thickness. The nanostratification observed in lanthanum manganites and required for GMR can be described taking into account the spread in TC in the CMR range δT.

Ground state properties of the one-dimensional quarter-filled strongly correlated electrons interacting with [formula omitted] Kondo spins

We study the ground state properties of the one-dimensional extended-Hubbard–Kondo model at quarter-filling. This model captures the essential feature of the π –d system of organic conductors where the strongly correlated electrons interact with localized S = 1 2 spins to bear interesting physics. It is shown that the charge ordered state realized in the strongly interacting region of electronic system is significantly stabilized by the introduction of antiferromagnetic Kondo coupling. This means that the charge degrees of freedom can be easily controlled by the magnetic field. From this, a new mechanism of giant magnetoresistance is proposed.

Mechanism of giant magnetoresistance in intermetallic compounds of rare-earth ions and actinides

Giant positive or negative magnetoresistance is calculated in a band model. The spectra of the band electrons in a two-sublattice antiferromagnetic intermetallic compound depend on the antiferromagnetism vector L(T,H). The metamagnetic transition to the ferromagnetic phase is accompanied by splitting with respect to the spin σ, displacement of the energy bands, and a decrease in the effective masses of the band electrons. This mechanism of giant negative magnetoresistance is also accompanied by an increase in the relaxation time τjσ. Scattering by chemical-bond fluctuations is considered as the main relaxation mechanism. Giant positive magnetoresistance results from a four-subband model of 4f and 5f intermetallic compounds. The electron effective masses m jσ(J jT ) of the (j,σ) bands increase with the mean angular momentum J 1T (T,H) of an ion in the jth sublattice of 4(5)f ions. The thermodynamics of such a four-sublattice model, the nonlinear magnetization and magnetoresistance curves, and the nonmonotonic dependence of the specific heat C m(T,H) on the field H are calculated.

Quantum well mechanism for giant magnetoresistance in trilayer

Mechanism of giant magnetoresistance in trilayer systems based on the infinite quantum well model has been suggested. The calculations of the exchange coupling and magnetoresistance as well as dependencies of these values on the thickness of ferromagnetic and nonmagnetic layers have shown the correlation between antiferromagnetic exchange coupling and giant magnetoresistance. The role of interface and bulk scattering on the giant magnetoresistance phenomenon has been discussed.

Mechanism of giant magnetoresistance in magnetic multilayers

Mechanism of giant magnetoresistance in magnetic multilayers

Influence of Au and Ag at the interface of sputtered giant magnetoresistance Fe/Cr multilayers

Multilayer films consisting of 20-AA Fe and 15-AA Cr with amounts of Au and Ag varying from 0 to 4 AA deposited at alternate Fe/Cr interfaces have been RF-diode-sputtered, and their magnetic and magnetotransport properties have been measured. When no noble metal is included, the films exhibit strong antiparallel coupling between adjacent Fe layers, with saturation fields as large as 7 kOe, and giant magnetoresistance (GMR) of 6% at 300 K, similar to that of MBE (molecular beam epitaxy)-grown films reported by others. The interruption of intimate contact between Fe and Cr at the interface resulting from noble-metal deposition gives rise to a substantial decrease in the magnitude of the GMR and the interfacial coupling. This suggests that the mechanism of GMR is associated with Fe and Cr in contact, as is required by models invoking spin-dependent impurity scattering. The results also suggest that the antiparallel coupling arises from direct exchange. >