Specific Heat of Field-dependent Magnetic Orderings in HoNi2B2C

Abstract

We have investigated the low-temperature specific heat of HoNi 2 B 2 C down to T = 1 K in various magnetic fields from 0 T to 5 T. At zero field, the specific heat exhibits a large peak at T N = 5.1 K, which is due to commensurate antiferromagnetic ordering, and other smaller peak at T 1 = 5.5 K, which is related to incommensurate ordering. As the field is increased up to 0.5 T, the first peak broadens and moves to a lower temperature, while the other peak at T 1 moves to a higher temperature, which indicates that the phase between T N and T 1 is more favored in magnetic fields. Among possible candidates for the phase, the a -axis modulation phase, which is an extension of a low temperature metamagnetic state, is the most probable. In the high-field region above 1 T, the two-peak feature is replaced by a broad-hill one that fades away with increasing fields, which is the typical smearing feature of the magnetic order at high fields.