Regular Article

Anisotropic giant magnetoresistive effect in the sandwich based Fe_xNi_1−x (x ≈ 0.5) and Cu

¹ Department of Electronics, General and Applied Physics, Sumy State University, 2 Rymskyi-Korsakov Street, 40007 Sumy, Ukraine
² Kharkiv National University of Civil Engineering and Architecture, 40 Sumska Street, 61002 Kharkiv, Ukraine

^a e-mail: y.shabelnyk@aph.sumdu.edu.ua

Received: 8 May 2018
Received in final form: 10 September 2018
Published online: 3 December 2018

Abstract

The anisotropic effect of a giant magnetoresistance (GMR) in the three-layer Fe_xNi_1−x/Cu/Fe_xNi_1−x/Sub (x ≈ 0.5, Sub is the substrate) magnetically ordered film is analyzed experimentally and theoretically using the phenomenological approach. It is shown that in the case when the direction of the current density vector j coincides with the direction of the local magnetization vector M (j∥M) in magnetic layers, the consideration of the resistance anisotropy results in a decrease in the magnitude of the GMR effect; and while the vectors are mutually perpendicular in the film plane (j⊥M), the GMR value increases. The analysis of the size dependence (dependence of the top magnetic layer on the thickness d_m2) of the magnetoresistance ratio (MR ratio) shows that, in the case of the isotropic GMR effect, when inequalities d_m2 << d_m1 (d_m2 >> d_m1) (d_m1 is the thickness of the bottom magnetic layer) hold, the indicated effect is negligible due to shunting of the top layer resistance by the base layer resistance (shunting of the base layer resistance by the top-layer resistance). In the case when the magnetic layer thicknesses are comparable in size (d_m1 ~ d_m2), the magnitude of the anisotropic giant magnetoresistance (AGMR) acquires its maximum (amplitude) value because of the absence of the shunting effect. The method for calculating the asymmetry parameter α_lj=l_0j⁺∕l_0j^– (l_0j^s is the spin-dependent free path of charge carriers in the s = ±th spin channel of the jth magnetic layer), which characterizes the difference in the free paths of electrons in the spin conduction channels, is proposed for the first time.