Unraveling the peculiar magnetic and electrical-transport properties of the structurally disordered half-Heusler alloy VCoGe

The structural, magnetic, and electrical-transport investigations of the polycrystalline half-Heusler VCoGe alloy are presented in this paper. In this compound, the DC magnetization behavior in the temperature range of 10-300 K produces the transition from the Pauli paramagnetism at normal temperature to a Curie-tail behaviour at low temperatures. The AC magnetic susceptibility confirms the magnetic anomaly observed in the low-temperature region, consistent with spin-lattice coupling behaviour. There is also a noticeable anomaly and a shift from a positive to a negative temperature coefficient of resistivity in the electrical resistivity measured in the temperature range of 10-320 K. Further electron spin resonance (ESR) experimental results highlight the spin-lattice coupling behaviour. The temperature-dependent peaks in the derivative microwave power as a function of the applied magnetic field appear as a broad line in the low-temperature region of the ESR data. We have performed the T=0 K density functional theory (DFT) calculations to determine the magnetic ground state and to explore the electronic structure of the VCoGe alloy. We have demonstrated semimetallic, antiferromagnetic (AFM) behaviour in the material using band-structure analysis and electronic density-of-states calculations. The phonon spectrum reveals the imaginary modes. The strong negative phonon density of states at low frequencies is mainly due to the vibrations of V and Ge atoms. The short-range antiferromagnetic (AFM) correlation, residual defects are the primary causes of the Curie-tail behavior. Since the crossover temperature of the resistivity transition is almost equal to the magnetic transition temperature, it can be assumed that in this compound, the spin-lattice coupling and short-range AFM correlation are the driving forces for the resistivity anomaly.