Magnetic anisotropy constants of ThMn12-type Sm(Fe1-xCox)12 compounds and their temperature dependence

The first and second-order uniaxial magnetic anisotropy constants K-1 and K-2 of the Sm(Fe1-xCox)(12) compounds and their temperature dependence are determined by the torque magnetometry technique using the anomalous Hall effect (AHE) on epitaxially grown Sm(Fe1-xCox)(12) thin films. While K-1 monotonically decreases with increasing temperature regardless of the Co concentration, K-2 changes its sign from negative to positive with increasing temperature and reaches a maximum at 250 K. These observations are consistent with the hard-axis magnetization curves at low temperature that show an upward deviation from a linear extrapolation of the low field part. Ab-initio estimations of the crystal field parameters at the Sm site using a spin model of Sm(Fe1-xCox)(12) compounds and theoretical analysis of magnetocrystalline anisotropy of Sm3+ ions taking the multiple J-mixing into account explain these main features of the experimental results.