Pressure-induced ferromagnetic order in the weak ferromagnet YbRhSb

Abstract

YbRhSb has a small spontaneous moment of 0.003 μB/Yb below Tm1= 2.7 K at ambient pressure. We have studied the pressure effect on the weak ferromagnetism by the measurements of dc magnetization for a single crystal up to 2.5 GPa. With increasing P, Tm1 (P) increases to a maximum value of 3.3 K. For 0.9 < P < 1.5 GPa, another magnetic transition occurs at Tm1 above Tm1, and Tm1(P) has a deep minimum of 2.5 K at PC = 1.7 GPa. For P > 2 GPa, a spontaneous moment of 0.3μB/Yb appears along the orthorhombic c-axis. In the ferromagnetic state above 2 GPa, magnetization curves for B ∥ a and B ∥ b exhibit sharp metamagnetic transitions at around 1.5 T. The complexity of the magnetic behaviors may be ascribed to the competition between single-ion crystal field anisotropy with easy direction ∥ a and inter-site exchange interaction with easy direction ∥ c.