Hall effect, resistivity, magnetoresistivity, and magnetic susceptibility measurements were performed on phosphorus (P)-doped ZnTe and ${\mathrm{Zn}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ single crystals with free-hole concentrations near the Mott critical density, $N_c=7.7\times {10}^{18}{\mathrm{cm}}^{-3}$ for ZnTe. The results reveal a temperature-driven metal-insulator transition (MIT) at a characteristic temperature $T_m$, accompanied by a paramagnetic-to-spin-glass phase transition. Above $T_m$, in the paramagnetic phase, electrical conductivity is dominated by nearest-neighbor hopping of holes within the impurity band. Below $T_m$, in the insulating spin-glass phase, the magnetic susceptibility increases and exhibits a positive Curie-Weiss temperature, $T_{\mathrm{CW}}=2.1\mathrm{K}$. In this regime, charge transport is governed by the hopping of small magnetic polarons within the Mn subsystem, leading to colossal negative magnetoresistance and pronounced magnetoresistive memory effects. These phenomena are interpreted in terms of charge-transfer coupling between ${\mathrm{Mn}}^{2+}$ ions and holes bound to ionized P acceptors, leading to the formation of ${\mathrm{Mn}}^{3+}$ ions and the electrical compensation of the acceptors. The coexistence of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Mn}}^{3+}$ gives rise to a ferromagnetic double-exchange interaction between ${\mathrm{Mn}}^{2+}\text{−}{\mathrm{Mn}}^{3+}$ pairs, which competes with the intrinsic antiferromagnetic superexchange between ${\mathrm{Mn}}^{2+}$ ions. This competition underlies the observed spin-glass behavior. These results provide insights into the interplay between hole transport and magnetic properties in diluted magnetic semiconductors near the MIT.

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• Doping effects
• Magnetic coupling
• Magnetic interactions
• Magnetotransport
• Polarons
• Spintronics
• Dilute magnetic semiconductors
• II-VI semiconductors
• Resistivity measurements
• Susceptibility measurements