Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGa₂O₄

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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. 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 Fe³⁺, 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.