Hole transport anomaly in high-TC ferromagnet (Zn,Mn)GeP2

Anomalous Hall effect and a large negative magnetoresistance (up to −8.5%) have been found in the high-TC ferromagnetic chalcopyrite (Zn,Mn)GeP2. The elevated manganese concentration in the top diffusion layer grown on ZnGeP2 isolated substrate gives rise to the increased hole conductivity and the temperature dependence of electric resistance ρ(T) typical of a metallic trace which indicate the charge carrier degeneration in combination with ferromagnetism. Additionally, we found a hysteresis of magnetoresistance Δρ/ρ0 vs. H is associated with change in a magnetic order at low temperatures, T<50 K. The effect accompanies the reversal sign of Δρ/ρ0 and is consistent with a singularity of magnetization vs. temperature. These anomalies observed for the first time in the high-TC ferromagnetic chalcopyrites II–IV–V2:Mn are explained by the phenomenological cluster model for ferromagnets.