Magnetoresistance in spinel-type MgxCu1−xCr2S4

CuCr2S4 shows a p-type metallic conductivity and ferromagnetism with Curie temperatures Tc of 375 K, and exhibit magnetic anomaly at 84 K (=Tm). CuCr2S4 exhibits the coexistence of both the ferromagnetism and spin-glass with the irreversible magnetic effect below Tm. The partial 20% Mg-substitution for Cu in CuCr2S4 slightly reduces the Tc and Tm. Magnetorsistance of MgxCu1−xCr2S4 can be expressed as Δρ=aH2−bHn below Tm. a, b, and n are temperature-dependent adjustable parameters. These unique MR behavior would be attributed to the coexistence of the ferromagnetism and spin-glass-like order below Tm. Mg-substitution decreased the conducting carrier, which forms the conduction band whose orbital motion gave the positive MR contribution. Therefore, Mg-substitution gave smaller positive MR contribution and consequently gave larger negative MR (maximum 7% at 10 K) in Mg0.2Cu0.8Cr2S4. These results suggest that Cr 3d band filling control can be expected to give functional magnetoelectric transport properties in CuCr2S4.