Transport Properties of NdB₆ Single Crystal under the Magnetic Fields up to 15 T

Abstract

We have studied the transport properties of NdB₆ single crystal under the magnetic fields up to 15, T between 2, K and 15, K. The Hall resistivity is constant in the paramagnetic region but shows an increase with decreasing temperature below T_N, which indicates the decrease of a carrier concentration in the antiferromagnetic (AF) state. This originates from the cut of the Fermi surface by super-zone in the AF state. Both resistivity ρ and specific heat exhibit roughly T² dependence below -- 6, K, being different from those expected for a usual AF metal. This suggests a finite contribution of magnons in ferromagnetic layers in the type I AF structure to low energy excitations of NdB₆. There exists no indication of the resistivity anomaly due to the AF ordering around T_N. In the paramagnetic region, ρ decreases and a thermal conductivity κ increases but a Lorentz number L decreases with increasing magnetic field. The former two properties originate from a suppression of large Q spin fluctuations by the magnetic field but the latter indicates that the inelastic spin-flip scattering becomes important with magnetic field. The magnetic field dependences of ρ, κ and L is very small in the AF state, which indicates that the probability of the spin-flip scattering is not changed by the magnetic field.