TRANSPORT-PROPERTIES OF NDB6 SINGLE-CRYSTAL UNDER THE MAGNETIC-FIELDSUP TO 15 T

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 resistiv ity is constant in the paramagnetic region but shows an increase with decreasing temperature below TN; which indicates the decrease of a car rier concentration in the antiferromagnetic (AF) state. This originate s from the cut of the Fermi surface by super-zone in the AF state. Bot h resistivity p and specific heat exhibit roughly T-2 dependence below similar to 6 K, being different from those expected for a usual AF me tal. This suggests a finite contribution of magnons in ferromagnetic l ayers in the type I AF structure to low energy excitations of NdB6. Th ere exists no indication of the resistivity anomaly due to the AF orde ring around T-N. In the paramagnetic region; p decreases and a thermal conductivity k increases but a Lorentz number L decreases with increa sing magnetic field. The former two properties originate from a suppre ssion of large Q spin fluctuations by the magnetic field but the latte r indicates that the inelastic spin-flip scattering becomes important with magnetic field. The magnetic field dependences of p, k and L is v ery small in the AF state, which indicates that the probability of the spin-flip scattering is not changed by the magnetic field.