Calculation of magnetic anisotropy energy in SmCo5

SmCo5 is an important hard magnetic material, due to its large magnetic anisotropy energy (MAE). We have studied the magnetic properties of SmCo5 using density functional theory (DFT) calculations where the Sm f-bands, which are difficult to include in DFT calculations, have been treated within the LDA+U formalism. The large MAE comes mostly from the Sm f-shell anisotropy, stemming from an interplay between the crystal field and the spin-orbit coupling. We found that both are of similar strengths, unlike some other Sm compounds, leading to a partial quenching of the orbital moment (f-states cannot be described as either pure lattice harmonics or pure complex harmonics), an optimal situation for enhanced MAE. A smaller portion of the MAE can be associated with the Co-d band anisotropy, related to the peak in the density of states at the Fermi energy. Our result for the MAE of SmCo5, 21.6 meV/f.u., agrees reasonably with the experimental value of 13-16 meV/f.u., and the calculated magnetic moment (including the orbital component) of 9.4 mu_B agrees with the experimental value of 8.9 mu_B.Comment: Submitted to Phys. Rev.

THE TEMPERATURE DEPENDENCE OF THE ANISOTROPY FIELD IN R2Fe14B COMPOUNDS (R = Y, La, Ce, Pr, Nd, Gd, Ho, Lu)

La variation thermique du champ d'anisotropie a été determinée dans les composés du type R2Fe14B (R = Th, Y, La, Ce, Pr, Nd, Gd, Ho, Lu) à des températures, entre 4.2 K et la température de Curie. Dans les composés Nd2Fe14B et Pr2Fe14B on a observé une réorientation du spin.The temperature dependence of the anisotropy field was measured in various compounds of the type R2Fe14B (R = Th, Y, La, Ce, Pr, Nd, Gd, Ho, Lu) at temperatures between 4.2 K and the Curie temperature. In Nd2Fe14B and Pr2Fe14B a spin reorientation was found to occur below room temperature