Structural-Phase State and Magnetotransport Properties of Thin Film Alloys Based on Permalloy and Copper

Abstract

The paper presents the results of research influence of composition on structural-phase state and magnetoresistive properties of as-deposited and heat-treated at temperatures Ta ≤ 900К samples film alloys based on Py and Cu. Samples of thin film alloys with a thickness of d  25 nm in the range of 19 ≤ cCu ≤ 69 (where cCu is the concentration of Cu, at.%) were obtained by the method of co-evaporation in vacuum from two independent evaporators. The structural-phase state of the samples of film alloys at cCu  19 at.%, 34 at.% and 61 at.% was investigated by the method of transmission electron microscopy. The structure of thin films in both as-deposited and annealed at Ta ≤ 900 K state consists of quasi granules with permalloy embedded in a nonmagnetic Cu matrix. The phase state of the samples at cCu  19 at.% and cCu  34 at.% in the as-deposited state and after heat treatment at Ta  600 K corresponded to fcc-NixFe (x ≈ 3) + fcc-Cu. After heat treatment at temperatures of 700  Ta  900 К, the phase state of the samples at cCu  19 at.% and cCu  34 at.% corresponded to Ni3Fe + fcc-Cu. For the film alloy sample at cCu  61 at.% in the as-deposited state and after heat treatment at temperatures of 600  Ta  900 К, the phase state corresponded to fcc-NixFe (x ≈ 3) + fcc-Cu. Studies of the magnetoresistive properties of film samples showed that the film samples in the entire range of compositions of 19 ≤ cCu ≤ 69 at.% were characterized by isotropic magnetoresistance. The maximum value of the giant magnetoresistance was observed for the sample with cCu  34 at.% Both in the as-deposited state and after heat treatment at temperatures of 600  Ta  900 К. Heat treatment of samples in the temperature range of 600  Ta  900 К had almost no effect on the value of GMR films at 19 ≤ cCu ≤ 51 at.%.