Showing papers on "Colossal magnetoresistance published in 1984"

Magnetoresistance studies of melt‐spun amorphous Fe1−xZrx ferromagnets

Abstract: A remarkable feature in amorphous Fe1−xZrx alloys is that for Fe concentrations greater than 90 at %, the ferromagnetic transition temperature TC decreases with increasing Fe concentration. In addition, alloys containing 93–90 at % Fe are found to show a spin‐glass‐like behavior at low temperatures, i.e., below TC. The electrical resistivity of these alloys shows a minimum at roughly the Curie temperature. We have measured the transverse magnetoresistance of Fe91Zr9, and Fe90Zr10 alloys from 4 to 300 K in applied magnetic fields as large as 9 T. We find that (1) the field derivative of the magnetoresistance is positive at all temperatures in applied fields larger than 0.1 T; (2) a maximum occurs in the magnetoresistance at roughly the Curie temperature; (3) below the Curie temperature a small negative low‐field magnetoresistance develops which increases with decreasing temperature. These results indicate that the resistance minimum which occurs around the Curie temperature for these alloys is due to the coherent exchange scattering by the Fe moments, and is not associated with a Kondo mechanism as previously proposed.A remarkable feature in amorphous Fe1−xZrx alloys is that for Fe concentrations greater than 90 at %, the ferromagnetic transition temperature TC decreases with increasing Fe concentration. In addition, alloys containing 93–90 at % Fe are found to show a spin‐glass‐like behavior at low temperatures, i.e., below TC. The electrical resistivity of these alloys shows a minimum at roughly the Curie temperature. We have measured the transverse magnetoresistance of Fe91Zr9, and Fe90Zr10 alloys from 4 to 300 K in applied magnetic fields as large as 9 T. We find that (1) the field derivative of the magnetoresistance is positive at all temperatures in applied fields larger than 0.1 T; (2) a maximum occurs in the magnetoresistance at roughly the Curie temperature; (3) below the Curie temperature a small negative low‐field magnetoresistance develops which increases with decreasing temperature. These results indicate that the resistance minimum which occurs around the Curie temperature for these alloys is due to the c...

Longitudinal magnetoresistance and temperature dependence of the electrical resistance of NiCr hydrides

Abstract: The transformation of ferromagnetic NiCr alloys with chromium contents between 0.5 and 7 at.% to a non-ferromagnetic hydride state leads to a minimum in the electrical resistance at low temperatures and to a negative contribution of the longitudinal magnetoresistance. This phenomenon can be understood, by analogy to the Kondo effect in dilute alloys, as the spin-flip scattering of conduction electrons at localized magnetic moments and its “freezing-out” by a magnetic field. Furthermore the results can be compared with those of other researchers on CuCr and non-dilute CuMn alloys.

Electric Field Influence on n‐GaAs Magnetoresistance in Impurity Conduction

Abstract: The effect of electric fields on the magnetoresistance of intermediately doped crystals (4 × 1015 ≦ ≦ ne ≦ 3 × 1016 cm−3) of n-type epitaxial gallium arsenide a t T = 4.2 K is studied. It is established that negative magnetoresistance is observed only in weak electric fields. Positive magnetoresistance is observed in an electric field higher than the impurity breakdown field. A transition from negative magnetoresistance to positive magnetoresistance is found to occur in an electric field less than the breakdown field. A model is suggested to explain magnetoresistance changes in electric fields, which takes into account the decrease of the negative component of magnetoresistance due to a decrease in the concentration of magnetic centres and the increase of the positive component due to the appearance of nonequilibrium carriers in the conduction band. [Russian Text Ignored].