Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGa${}_2$O${}_4$

Abstract

Solid solutions of nominal composition [ZnGa${}_2$O${}_4$]${}_{1-x}$[Fe${}_3$O${}_4$]${}_x$, of the semiconducting spinel ZnGa${}_2$O${}_4$ with the ferrimagnetic spinel Fe${}_3$O${}_4$ 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. Magnetization as a function of field for the $x$ = 0.15 sample is S-shaped at temperatures as high as 200 K. Mössbauer spectroscopy on the $x$ = 0.15 sample confirms the presence of Fe${}^{3+}$, and spontaneous magnetization at 4.2 K. The magnetic behavior 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 the possibility of dilute ferrimagnetic semiconductors which do not require carrier mediation of the magnetic moment.

9 pages and 6 figures