Comparison of Electronic and Magnetic Properties of 4d Transition Metals Based NbAl2F4 and TcAl2F4 Spinels

Half-metallic properties of NbAl2F4 spinel and semiconductor characteristics of TcAl2F4 spinel were investigated with the help of the WIEN2k program. NbAl2F4 spinel shows a metallic character in the up-electron states, while it has a semiconductor nature in the down-electron states. In NbAl2F4 spinel, the Eg bandgaps were calculated in GGA and GGA+mBJ 1.551 eV and 1.622 eV, respectively. The EHM half-metallic bandgaps were obtained 0.410 eV and 0.422 eV, respectively. In the up-spin states of TcAl2F4 spinel, Eg values were obtained 1.199 eV and 1.447 eV for the GGA and GGA+mBJ methods, respectively, while they were obtained 1.281 eV and 1.519 eV in the down-spin states, respectively. When GGA+mBJ is used, it is easily observed that the semiconductor characters increase. Total magnetic moments of NbAl2F4 and TcAl2F4 spinels were calculated 6.00 µB/cell and 10.0 µB/cell, respectively. When both electronic and magnetic moment values are carefully examined, NbAl2F4 and TcAl2F4 spinels can be used as alternative compounds in spintronic applications.