Nonlinear magnetoelastic coupling coefficients in Fe from an ab initio calculation

Based on the nonlinear theory of magnetoelasticity, a general method is developed which allows the determination of first-order and second-order magnetoelastic coefficients of a magnetic material from the ab initio calculation of magnetocrystalline anisotropy energies as functions of various modes of imposed strain. Explicit results are given for BCC Fe. The data confirm the hints from the magnetostrictive stress experiments that nonlinear magnetoelastic coupling effects are essential for the magnetic properties of thin epitaxial magnetic films with large epitaxial strains.