Effect of pressure on the field-induced ordered phase in the heavy-fermion compound YbCo2Zn20

The effect of pressure on the field-induced ordered phase for H ‖ 〈111〉 in the heavy-fermion compound YbCo 2 Zn 20 , which is presumably a field-induced antiferro-quadrupolar (FI-AFQ) phase, was investigated in the pressure range up to 4.5 GPa and under magnetic fields up to 80 kOe. When pressure is applied, the metamagnetic-like transition at H m =6 kOe shifts to lower fields and disappears around the quantum critical pressure P c ∼1.8 GPa. A pressure-induced antiferromagnetic (PI-AFM) phase appears at pressures above about 2 GPa, and the critical field H c of the PI-AFM phase increases with increasing pressure. On the other hand, the transition field H Q of the FI-AFQ phase decreases gradually without showing any anomalous behavior around P c and becomes obscure around 4 GPa, where H c of the PI-AFM phase and H Q of the FI-AFQ phase become comparable. The magnetic field versus pressure, H - P , phase diagram for H ‖ 〈111〉 at 0.1 K was constructed in the pressure range up to 4.5 GPa.