Structural stability, electronic and magnetic properties of a new Rb ₂ TiZ (Z = Si, Ge, Sn and Sb) Full Heusler alloys: a DFT approach

In the present work, we investigated a new series of full-Heusler magnetic semiconductor alloys, Rb₂TiZ (Z = Si, Ge, Sn, and Sb), focusing on their structural, electronic, and magnetic properties using first-principles calculations. The computations were performed within the framework of the full-potential linearised augmented plane wave (FP-LAPW) method, employing the generalised gradient approximation (GGA) and the modified Becke – Johnson (mBJ) potential. For the most stable configuration, namely the ferromagnetic Hg₂CuTi-type structure, all compounds were found to be mechanically, thermodynamically, and dynamically stable. The calculated magnetic moments of these compounds follow the Slater – Pauling rule, Mt = (Zt – 8) μB. According to the band structure profiles, all compounds exhibit a finite band gap in both spin channels. For the majority-spin states, the band gaps are 1.133, 0.922, 1.068, and 0.024 eV, whereas for the minority-spin states they are 1.248, 1.022, 1.180, and 2.184 eV, for Rb₂TiSi, Rb₂TiGe, Rb₂TiSn, and Rb₂TiSb, respectively. The total and partial density of states analyses reveal that p–d hybridisation plays a crucial role in the formation of the band gap. The effects of spin–orbit coupling (SOC) on the electronic and magnetic properties of Rb₂TiZ full Heusler alloys were investigated. Our findings suggest that SOC has an insignificant impact on the electronic characteristics, with the band gap largely preserved. Furthermore, the estimated values of the exchange splitting energy and the high Curie temperatures suggest that these alloys are promising candidates for spin-filter technology.