Ferromagnetic Semiconductor In_0.75Fe_0.25Sb for All-Optical Control of Light Polarization

In this work, we investigate highly iron-doped indium antimonide, whose electronic structure is favorable for use in ultrafast magneto-optical devices. Density functional theory (DFT) calculations show that the incorporation of 25% Fe into InSb gives rise to a degenerate n-type ferromagnetic semiconductor. A high concentration of spin-polarized electrons around the Fermi level and spin splitting of the Fe 3d orbitals with asymmetric occupation of the orbital states due to hybridization with Sb 5p orbitals create a conduction band. Hybridization, with a significant contribution of magnetic moment in interstitial regions, stabilizes the ferromagnetism in the zinc-blende structure. The peculiar bulk inversion asymmetry (BIA) of this structure determines the existence of an intrinsic magnetocrystalline anisotropy with the easy magnetization axis along the crystallographic [111] axis, the only preserved inversion symmetry axis. The intraband transitions between spin-split Fe 3d orbitals generate magnetic circular dichroism and the Kerr effect with rotation reversals and ellipticity in the visible region (1.8 and 2.5 eV) that enable applications in ultrafast devices based on the spin-transfer torque phenomenon and all-optical tunable magnetic Kerr gates based on Kerr dispersion.