Hysteresis of the variable range hopping magnetoresistance in the moderately compensated p-type Ge

The magnetoresistance hysteresis phenomenon has been discovered in the regi me of variable range hopping via Coulomb gap states in moderately compensat ed p-type Ge:Ga after a premagnetization at several kOe. A series of sample s was prepared by neutron transmutation doping of pure Ge and covered a wid e doping range including the metal-insulator transition. In a critical fiel d of about 700 Oe the hysteresis is accompanied by a sharp resistivity drop , characterized by a well pronounced maximum for a doping level of 0.4 on t he insulator side of the metal-insulator transition. The drop is created by the energy output overheating during the remagnetization of the initially magnetized sample. Possible mechanisms of the initial magnetization are dis cussed.