Calculated trends of the magnetostriction coefficient of 3d alloys from first principles

The general behavior of the magnetostriction coefficients for Fe, Co, and Ni and their alloys is reproduced by first-principles theory. It is shown that the low magnetostriction coefficient of soft magnetic materials, observed for specific alloy concentrations, such as permalloy, can be explained theoretically by employing relativistic first-principles calculations in combination with the rigid-band approximation. The connection between magnetostriction and magnetocrystalline anisotropy is discussed as well as the physical mechanisms behind soft magnetic materials. Theory is hence demonstrated to have the ability of predicting values of the magnetostriction coefficient of any alloy, and a microscopic understanding of this entity is starting to emerge.