Electronic structure and magnetic properties of the ThCo4B compound

Detailed theoretical investigations of the electronic and magnetic properties of the newly discovered ThCo4B compound have been performed. The influence of the local environment on the magnitude of the Co magnetic moments is discussed by comparing the magnetic and electronic properties in the ThCo4B, YCo4B and ThCo5 systems. All theoretical investigations of the electronic and magnetic properties have been done using the Korringa-Kohn-Rostoker (KKR) band-structure method in the ferromagnetic state. Very good agreement of the calculated and the experimental magnetic moments is obtained. Larger exchange-splitting is observed on the 2c site which carries by far the largest magnetic moment. Comparison of the band structure calculation for ThCo5 and ThCo4B reveals that the presence of boron in the Co 6i site environment induces a broadening of the electronic bands as well as a significant reduction of the exchange-splitting and a diminution of the DOS at the Fermi level. These differences are attributed to the hybridization of the boron electronic states to the cobalt 3d ones. The calculated magnetic moment is 1.94 mu(B)/formula unit. A large difference on the magnetic moment magnitude of the two Co sites is observed since 1.30 and 0.27 mu(B)/atom are calculated for the 2c and 6i sites, respectively. The orbital contribution is found to differ by almost an order of magnitude on both cobalt sites. The Co magnetic moment is much smaller in the ThCo4B than in the YCo4B or RCo4B (where R is a rare earth) isotypes evidencing the major role played by the Th-Co bands on the electronic properties. (C) 2007 Elsevier B.V. All rights reserved.