Magnetostriction Behaviors of Fe_{100–<i>x</i>}Co_<i>x</i> Alloy Epitaxial Thin Films under Rotating Magnetic Field

Abstract

Fe 100-x Co x (x = 0, 30, 50 at. %) alloy thin films are prepared on MgO substrates of (001), (110), and (111) orientations by ultra-high vacuum magnetron sputtering. The influences of film orientation and composition on the magnetic anisotropy and the magnetostriction are investigated. Fe 100-x Co x (001) single-crystal and (211) bi-crystal films are respectively obtained on MgO(001) and (110) substrates. Fe 100-x Co x (110) films are epitaxially grown on MgO(111) substrates with two types of variants with the crystallographic orientation relationships similar to Nishiyama-Wasserman and Kurdjumov-Sachs. The (001) single-crystal and the (211) bi-crystal films, respectively, show four-and twofold symmetric in-plane magnetic anisotropies, which are reflecting the magnetocrystalline anisotropy of Fe 100-x Co x crystal with the easy magnetization axes parallel to <100> or <111>. On the contrary, isotropic in-plane magnetization properties are observed for the (110) films due to an influence of the variant structure. The magnetostriction is measured under rotating magnetic field by using a cantilever method. As the Co content increases from 0 to 50 at. %, the magnetostriction coefficients, λ 100 and λ 111 , respectively increase from +10-5 to +10-4 and from-10-5 to +10-5 for both Fe 100-x Co x (001) single-crystal and (211) bi-crystal films. Large λ 100 values are also indicated for the Fe 100-x Co x (110) epitaxial films (x = 30, 50). The present study shows that it is possible to obtain large magnetostriction of 10-4 by control of the film orientation and composition.