Analysis of the co‐doping effect of manganese and lanthanide elements in SrGa2S4 by the relativistic DV‐Xα calculation

Abstract

AbstractThe electronic states of manganese and lanthanide elements in SrGa2S4 are calculated by the relativistic discrete variational Xα method using a FORTRAN program of DVSCATR in order to investigate the mechanism allowing the 3d‐3d transition of Mn in SrGa2S4 by co‐doping a lanthanide element. We use a spherical cluster model of the D2 symmetry which consists of 45 atoms of Sr9Ga12S24, representing SrGa2S4, in our calculation. Doping a lanthanide to SrGa2S4 is represented by substituting a Sr atom with a lanthanide atom (indicated by ‘Ln’) at the cluster centre as (LnSr8)Ga12S24. Two types of co‐doping models are prepared as (LnMn2Sr6)Ga12S24 for MnSr and (LnSr8)(Mn4Ga8)S24 for MnGa with keeping the D2 symmetry. As a result of the self‐consistent charge (SCC) calculation, the averaged distance between a lanthanide atom at the cluster centre and surrounding eight sulphur atoms has to be set as 70 to 80% of that between the original Sr‐S combinations. Calculated electronic states show that the Ln(5d) and Mn(4s,4p) atomic orbitals are highly mixed, and in the lower energy range, the Mn(4s,4p) and Mn(3d) are also highly mixed. This hybridization cascade can explain the co‐doping effect as that the electrons optically excited to the unoccupied states relating to the Ln(5d) would finaly relax to the 3d‐3d transition of Mn. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)