Study of the electrophysical and magnetic properties of a Dirac 3D semimetal Cd3As2 with nanogranules of MnAs

Abstract

We report on the main results of studying the electrical and magnetoresistance (MR) of a composite material consisting of 70 % mol. Dirac semi-metal Cd3As2 and 30 % mol. ferromagnet MnAs at pressures up to 50 GPa in a diamond anvil cell with a «rounded cone-flat» type anvils, as well as magnetization at hydrostatic pressures up to 6 GPa in a toroid-shaped high-pressure cell, both at room temperature and in the temperature range of 180 – 350 K at atmospheric pressure. A mixture of methanol and ethanol in a ratio of 4:1 was used as a pressure transmitting medium. Elemental analysis of Cd3As2 + 30 % mol MnAs composites showed that much of the volume is occupied by the Cd3As2 phase. The proportion of MnAs phase inclusions is less than 5 %. The feature of Cd3As2 + MnAs is the presence of a significant region of non-mixing of the Cd3As2 and MnAs phase melts. A negative MR was revealed with increasing pressure in the entire studied baric zone. The maximum negative MR is observed in the baric zone of 22 – 26 GPa. Further increase in the pressure up to the maximum level result in the appearance of several extrema on the ΔR/R0(P) curve, with negative MR not exceeding 4 %. Upon pressure release from 50 GPa, the baric dependence of ΔR/R0(P) is characterized by an inversion of the MR sign: at pressures around 40 GPa, a negative MR is replaced by a positive MR, and at around 20 GPa, the maximum value of positive MR of ~5.3 % is observed. Signs of the instability of the monoclinic structure of Cd3As2 resulted from its partial decomposition upon decompression were revealed. The results obtained can be used in spintronics when using appropriate composite materials.