Thermoelectric Properties of Layer-Antiferromagnet CuCrS_(2)

摘要

We have performed a detailed study of the electrical and thermal conductivities and thermoelectric power behavior of an antiferromagnetic-layer compound of chromium, CuCrS_(2), from 15 K to 300 K. Unlike previous studies, we find noninsulating properties and sensitive dependence on the preparation method, the microstructure, and the flaky texture formed in polycrystalline samples after extended sintering at high temperatures. Flakes are found to be metallic, with strong localization effects in the conductivity on cooling to low temperatures. The antiferromagnetic transition temperature TN (velence40 K) remains essentially unaffected. The Seebeck coefficient is found to be in the range of 150 (mu)V/K to 450 (mu)V/K, which is exceptionally large, and becomes temperature independent at high temperatures, even for specimens with low resistivity values of 5 m(OMEGA) cm to 200 m(OMEGA) cm. We find the thermal conductivity kappa to be low, viz. 5 mW/K cm to 30 mW/K cm. This can be attributed mostly to the dominance of lattice conduction over electronic conduction. The value of kappa is further reduced by disorder in Cu occupancy in the quenched phase. We also observe an unusually strong dip in kappa at T_(N), which is probably due to strong magnetocrystalline coupling in these compounds. Finally we discuss the properties of CuCrS_(2) as a heavily doped Kondo-like insulator in its paramagnetic phase. The combination of the electronic properties observed in CuCrS_(2) makes it a potential candidate for various thermoelectric applications.