Competition between the Quadrupole Interaction and Crystalline Electric Field Effect in the Antiferromagnetic Ordered Phase of NdB₆

Abstract

We have studied the thermal and transport properties of NdB₆ focused on the anisotropic behaviors depending on the applied magnetic field direction. The magnetic field dependence of the physical properties in the type-I antiferromagnetic phase is small for H||[001] or [110] but is large for H||[111]. These anisotropic behaviors are associated with the different domain distribution depending on the applied magnetic field direction. For H||[001] or [110], the domain with only the χ_⊥ component is realized, and for H||[111], that with both the χ_⊥ and χ_|| components is realized, where the competition among the crystalline electric field effect leading to the three-fold easy axis and the O₂⁰-type ferro-quadrupole interaction leading to the four-fold easy axis and also the antiferromagnetic interaction plays an important role. This competition might be important for the appearance of the successive metamagnetic phase transitions for H||[111]. The anisotropic behaviors of the magnetization, the specific heat and the electrical resistivity depending on the applied magnetic field direction in the type I-AFMI phase were analized by the mean field calculation by considering the different domain distribution depending on the magnetic field direction and could explain the characteristics of these anisotropic behaviors in low magnetic field region in the AFMI phase rather well.