We investigate the distribution of element-specific magnetic moments and changes in the spin-resolved unoccupied density of states in a series of half-metallic ${\text{Co}}_2\left({\text{Mn}}_x{\text{Ti}}_{1-x}\right)\text{Ge}$ Heusler alloys using x-ray magnetic circular dichroism. The Co and Mn magnetic moments are oriented parallel while a small Ti moment shows antiparallel to the mean magnetization. The element-specific magnetic moments remain almost independent on the composition. Therefore, a replacement of Ti by Mn results in an increase in magnetization. The increase in magnetization with increasing $x$ follows the Slater-Pauling rule. The Fermi level decreases with respect to the minority band gap with increasing number of valence electrons. This counterintuitive behavior is explained qualitatively by a charge transfer model and quantitatively by ab initio band-structure calculations.

• Received 14 July 2010

DOI:https://doi.org/10.1103/PhysRevB.82.104410