Anisotropy in magnetoelastic effects of YCo5

We develop the phenomenological theory for uniaxial ferromagnets and derive explicit formulas for their magnetostriction (MS) and magnetic anisotropy energy (MAE) generated by the magnetoelastic (ME) effects. An analysis of the experimental results for the MS in hexagonal YCo5 using the formulas obtained reveals that (1) an elastic anomaly should appear in the elastic constant c33, and (2) the MAE caused by the ME effects could be non-negligible. The calculated results of the electronic structure under lattice deformation indicate that the particular arrangement of Co atoms in the lattice is related to the anisotropy of MS in YCo5. It is suggested that the anisotropic MS observed for various Y compounds could be interpreted in a similar manner.