Magnetic Ordering in TlGa1-xFexSe2 Dilute Magnetic Semiconductors with Various Fe Dilution Ratios

Abstract

The results of the studies of structural and magnetic properties of Fe-doped \({\mathrm{TlGaSe}}_{2}\) (\({\mathrm{TlGa}}_{1-\mathrm{x}}{\mathrm{Fe}}_{\mathrm{x}}{\mathrm{Se}}_{2}\)) layered magnetic semiconductor grown with two different doping concentrations (\(x\)) are presented. Electron paramagnetic resonance (EPR) investigations revealed that Fe³⁺ ions are located at the centers of GaSe₄ tetrahedra formed by Se atoms and the site symmetry around Fe³⁺ 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 (\({\lambda }^{^{\prime}}\)) estimated from magnetization and EPR measurements of \({\mathrm{TlGa}}_{1-\mathrm{x}}{\mathrm{Fe}}_{\mathrm{x}}{\mathrm{Se}}_{2}\) 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 \({\mathrm{TlGaSe}}_{2}\) four-layer slab were explored using density functional theory (DFT) calculations. We have found that substituting \(\mathrm{Fe}\) single dopant atom at the \(\mathrm{Ga}\) site, and the formation of substitutional \({\mathrm{FeSe}}_{4}\) complexes due to the strong hybridization between the electronic states of the dopants and the neighboring \(\mathrm{Se}\) atoms are geometrically and energetically favorable for \({\mathrm{TlGa}}_{1-\mathrm{x}}{\mathrm{Fe}}_{\mathrm{x}}{\mathrm{Se}}_{2}\). Our calculations indicate that the magnetic coupling between Fe dopants and the neighboring \(\mathrm{Se}\) 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 Fe³⁺ ions in \({\mathrm{TlGa}}_{1-\mathrm{x}}{\mathrm{Fe}}_{\mathrm{x}}{\mathrm{Se}}_{2}\) compounds are important experimental confirmations of theoretical predictions. The saturation magnetization for \({\mathrm{TlGa}}_{1-\mathrm{x}}{\mathrm{Fe}}_{\mathrm{x}}{\mathrm{Se}}_{2}\) compound is found to increase with increasing of the Fe³⁺ dopant concentration.