Study on the magnetic origin in p-type ferromagnetic semiconductor (Ga,Fe)Sb: ab initio calculations

The electronic and magnetic properties of Ga 1− x Fe x Sb ( x =0.125, 0.25, 0.5) have been investigated using the first-principles calculations based on density functional theory (DFT) and DFT plus on-site repulsion scheme (DFT+U). We found that the Coulomb U parameter plays an important role in predicting the correct stable magnetic order. Using the DFT+U method, the ferromagnetic (FM) ordering is found to be the magnetic ground state for both concentrations 12.5% and 25%, where the DFT failed without on-site repulsion U-term correction. This failure of semi-local DFT functionals is the fingerprint of the correlated nature of Fe-3d electrons. This result is in good agreement with experiment. Increasing Fe concentration up to 50% changing the magnetic ground state from FM to antiferromagnetic (AF) phase. We have used the Heyd-Scuseria-Ernzerhof (HSE) method to calculate the unfolded band structure of supercell for Ga 1− x Fe x Sb for x =0.125, in both FM and AF phases. The location of Fe-3d states in the calculation of the unfolded band structure showed a good accordance with recent resonance photoemission spectroscopy (RPES) experimental results. We have found that hole carriers have an important role at Fermi level E F . The rules of thumb to predict the stability of the ferromagnetism in Fe doped GaSb FMS have been discussed.