Monday, June 24, 2013

1210.1991 (Samuel Tardif et al.)

Toward an accurate modeling of x-ray magnetic circular dichroism in
(Ge,Mn) compounds

Samuel Tardif, Andrey Titov, Emmanuel Arras, Ivetta Slipukhina, El-Kebir Hlil, Salia Cherifi, Yves Joly, Matthieu Jamet, André Barski, Joel Cibert, Erkin Kulatov, Y. A. Uspenskii, Pascal Pochet
X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) spectra at the L$_{2,3}$ edges of Mn in different (Ge,Mn) compounds are calculated from first principles. Early \textit{ab initio} studies show that the Density Functional Theory (DFT) does not reproduce a characteristic change of sign in the L$_{3}$ XMCD spectrum of Mn in Ge$_3$Mn$_5$, which is observed in experiment. In this work we demonstrate that this disagreement is partially related to an underestimation of the exchange splitting of Mn 2$p$ core states within the local density approximation. It is shown that the change in sign experimentally observed is reproduced if the exchange splitting is calculated within the Hartree-Fock approximation, while the final states can be still described by the DFT. This approach is further used to calculate the XMCD in different (Ge,Mn) compounds. It demonstrates the high sensitivity of XMCD, compared to XAS, to the local atomic structure around Mn absorbers.
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