Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment inL10-Type Ordered and Disordered Alloys

Abstract

The magnetocrystalline anisotropy energy and orbital magnetic moment in L 1 0 -type transition metal alloys such as FePt, FePd, FeNi, CoPt, CoPd, and MnAl are evaluated while continuously varying the degree of order. The electronic structure with spin–orbit interaction is calculated by employing the tight-binding linear muffin-tin orbital method based on the local spin-density approximation. To control the degree of order, we consider a substitutional disorder and then adopt the coherent potential approximation. The magnetocrystalline anisotropy energy Δ E is roughly proportional to the power of the long-range order parameter S , i.e., Δ E ∝ S n ( n ∼1.6–2.4). We also discuss the relationship between the magnetocrystalline anisotropy energy and the orbital magnetic moment. In the same compositional system with different degrees of order, the difference between the orbital magnetic moment in the magnetic easy axis and that in the hard one is proportional to Δ E . However, the coefficient corresponding to the effective spin–orbit coupling is inconsistent with the intrinsic one in some cases.