Enhancement of the spin-glass transition temperature through pd -orbital hybridization in Zn1−xMnxTe

Abstract

To gain insight into the spin-glass state of diluted magnetic semiconductors, we have examined the magnetic and electronic properties of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ using density-functional theory as well as performed magnetization measurements on the $x=0.43$ and 0.55 systems to demonstrate a clear spin-glass transition consistent with previous literature. Using a generalized gradient approximation, we investigate the electronic and magnetic properties for $x=0$, 0.075, 0.15, 0.25, and 0.50 doping levels using the magnetic moment of ${\mathrm{Mn}}^{2+}$ as guide for the dependence of the Hubbard onsite potential on the electronic structure. Simulations on both ferromagnetic (FM) and antiferromagnetic (AFM) configurations yield a distinct AFM ground-state preference, which is consistent with a zero-magnetic-moment spin-glass state. Here an onsite potential of up to 8 eV on the Mn $3d$ orbitals is needed to harden the magnetic moment toward $S=5/2$. From our analysis of the electronic structure evolution with doping and onsite potential, we confirm the semiconducting state of the Mn-doped ZnTe as well as show that the presence of Mn incorporated into the ZnTe matrix at the Zn lattice site produces magnetic interactions through the Te ions with a distinct Te-Mn $pd$-orbital hybridization. Furthermore, we show that this hybridization is activated with the Mn doping above 0.25 concentration, which corresponds to the doping level in which the spin-glass transition begins to rise. Therefore, it is likely that the coupling of $pd$-orbital hybridization of the Mn and Te $p$ orbitals is a precursor to the enhancement of the spin-glass transition temperature.