Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGa2O4

Solid solutions of nominal composition [ZnGa2O4](1-x)[Fe3O4](x), of the semiconducting spinel ZnGa2O4 with the ferrimagnetic spinel Fe3O4, have been prepared with x = 0.05, 0.10, and 0.15. All samples show evidence for long range magnetic ordering with ferromagnetic hysteresis at low temperatures. The magnetization as a function of field for the x = 0.15 sample is S-shaped at temperatures as high as 200 K. Mossbauer spectroscopy of the x = 0.15 sample confirms the presence of Fe3+, and spontaneous magnetization at 4.2 K. The magnetic behaviour is obtained without greatly affecting the semiconducting properties of the host; diffuse reflectance optical spectroscopy indicates that Fe substitution up to x = 0.15 does not affect the position of the band edge absorption. These promising results motivate us to suggest the possibility of dilute ferrimagnetic semiconductors which do not require carrier mediation of the magnetic moment.