Magnetostriction Behaviors of Fe100–xCox Alloy Epitaxial Thin Films under Rotating Magnetic Field

Fe100–xCox (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. Fe100–xCox(001) single-crystal and (211) bi-crystal films are respectively obtained on MgO(001) and (110) substrates. Fe100–xCox(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 two-fold symmetric in-plane magnetic anisotropies, which are reflecting the magnetocrystalline anisotropy of Fe100–xCox crystal with the easy magnetization axes parallel to or . 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, λ100 and λ111, respectively increase from +10–5 to +10–4 and from –10–5 to +10–5 for both Fe100–xCox(001) single-crystal and (211) bi-crystal films. Large λ100 values are also indicated for the Fe100–xCox(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.