Abstract
Systematic trends in the magnetism of Co-Pt solid-state systems are explored by studying the effects of composition, electron correlations, spin-orbit coupling (SOC), and long-range order. Ab initio fully relativistic calculations were performed for bulk Co, a substitutional Pt impurity in Co, , CoPt, , and a substitutional Co impurity in Pt. Many-body effects beyond the local spin-density approximation (LSDA) were included via the dynamical mean-field theory (DMFT); a comparison with results based on the Brooks orbital-polarization (OP) scheme was also made. The disorder was treated within the coherent-potential approximation. We found that while the spin magnetic moments at the Co atoms monotonously increase with increasing Pt concentration, the orbital magnetic moments do not follow the trend of . Magnetic moments and at Pt atoms do not depend on Pt concentration monotonously. Most of these trends can be understood in terms of hybridization and site-dependent SOC. The OP scheme of Brooks corrects the deficiencies of a pure LSDA only if the Pt concentration is low. The scheme provides ratios for Co atoms which agree with experiment even for high Pt content. Introducing disorder leads to an enhancement of at Co atoms and to a suppression of at Pt atoms. The at Co atoms does not exhibit any systematic dependence on the degree of order, while at Pt atoms decreases with increasing disorder for all Pt concentrations.
- Received 10 July 2008
DOI:https://doi.org/10.1103/PhysRevB.78.144403
©2008 American Physical Society