Magnetic properties of SmCo5 and YCo5

Abstract

We have studied the magnetic moments and magnetic anisotropy energy (MAE) of YCo5 and SmCo5 using full-potential linear augmented plane wave (LAPW) electronic structure calculations. Most previous calculations of the MAE for YCo5, using local density approximation (LDA) for the exchange-correlation potential, have found values significantly smaller (∼0.6 meV/f.u.) than experiment (∼3.8 meV/f.u.). The rest of the MAE is attributed to many body corrections. Our LAPW calculations using the generalized gradient approximation (GGA) instead of LDA and including nonspherical corrections give values ∼1.5 meV/f.u. The Co magnetic moment of YCo5−xCux, unlike the prediction of the virtual crystal approximation, decreases slowly with impurity concentration until dropping suddenly to zero at a critical dopant concentration. Correlation effects were found to be crucial for the MAE in SmCo5. While GGA calculations give MAE for SmCo5 of the wrong sign, including the LDA+U, correction brings it to ∼21 meV/f.u., in good agreement with the experimental value of 13–16 meV/f.u.