Multiple magnetic transitions and magnon gaplike characteristics in the high purity TbB4 single crystal

Abstract

We synthesized the high purity TbB4 single crystal, which shows quite low resistivity at T=2 K, rho(T=2 K)=0.0397 mu Omega cm, resulting in a high residual resistivity ratio RRR equivalent to rho(300 K)/rho(2 K)=361.9. Because of the geometry of the grown single crystals, temperature-dependent magnetization M(T) was measured with applied magnetic field parallel to (010) and (111) planes. M(T) was found to be anisotropic at high temperature and revealed two magnetic transitions: one is antiferromagnetic transition at T-N=44 K and the other one at T-m approximate to 23 K for both field orientations. These transitions were also manifested by the slope change of temperature-dependent resistivity, i.e., d rho(T)/dT. The second transition temperature T-m was found to decrease and the transition width broadened with increasing applied magnetic field, indicating that the transition at T-m is suppressed by applied magnetic field. The Fermi liquid and antiferromagnetic (AF) magnon gaplike increase of rho(T) was found at low temperatures of T <= 20 K. The AF magnon gap Delta=15.6 K at H=0 T was also found to decrease with applying magnetic fields. We will discuss the origin of the second transition T-m in terms of the interaction between magnetic and quadrupolar orbital fluctuations.