Magnetic Ordering in TlGa 1-x Fe x Se 2 Dilute Magnetic Semiconductors with Various Fe Dilution Ratios

The results of the studies of structural and magnetic properties of Fe-doped TlGaSe_2 ( TlGa_1-xFe_xSe_2 ) layered magnetic semiconductor grown with two different doping concentrations ( x ) are presented. Electron paramagnetic resonance (EPR) investigations revealed that Fe 3+ ions are located at the centers of GaSe 4 tetrahedra formed by Se atoms and the site symmetry around Fe 3+ centers are orthorhombic. The crystal field parameters of the structure have been calculated by fitting the orthorhombic spin Hamiltonian using rotation patterns of EPR spectra. The crystal field parameters and rhombicity ratio ( λ^^' ) estimated from magnetization and EPR measurements of TlGa_1-xFe_xSe_2 crystals are found to be larger and lower for samples with higher and lower dilution ratios respectively. Structural stability, electronic and magnetic properties of the Fe-doped TlGaSe_2 four-layer slab were explored using density functional theory (DFT) calculations. We have found that substituting Fe single dopant atom at the Ga site, and the formation of substitutional FeSe_4 complexes due to the strong hybridization between the electronic states of the dopants and the neighboring Se atoms are geometrically and energetically favorable for TlGa_1-xFe_xSe_2 . Our calculations indicate that the magnetic coupling between Fe dopants and the neighboring Se atoms is dominantly ferromagnetic. While weakly antiferromagnetic interactions between Fe–Fe dopants due to the super-exchange mechanism is favorable. The positive value of the Curie temperature together with the observed antiferromagnetic hysteresis loops as well as with the characteristic temperature dependence of magnetic susceptibility indicate the existence of combined antiferromagnetic and weak ferromagnetic ordering between interacting unpaired spin orbitals of Fe 3+ ions in TlGa_1-xFe_xSe_2 compounds are important experimental confirmations of theoretical predictions. The saturation magnetization for TlGa_1-xFe_xSe_2 compound is found to increase with increasing of the Fe 3+ dopant concentration.