Specific heat of CeRhIn5 in high magnetic fields: Magnetic phase diagram revisited

S. Mishra, A. Demuer, D. Aoki, I. Sheikin
2021 Physical review B  
CeRhIn_5 is a prototypical antiferromagnetic heavy-fermion compound, whose behavior in a magnetic field is unique. A magnetic field applied in the basal plane of the tetragonal crystal structure induces two additional phase transitions. When the magnetic field is applied along, or close to, the c axis, a new phase characterized by a pronounced in-plane electronic anisotropy emerges at B^* ≈ 30 T, well below the critical field, B_c ≃ 50 T, to suppress the antiferromagnetic order. The exact
more » ... of this new phase, originally suggested to be an electronic-nematic state, remains elusive. Here we report low-temperature specific-heat measurements in CeRhIn_5 in high static magnetic fields up to 36 T applied along both the a and c axes. For fields applied along the a axis, we confirmed the previously suggested phase diagram, and extended it to higher fields. This allowed us to observe a triple point at ∼ 30 T, where the first-order transition from an incommensurate to commensurate magnetic structure merges into the onset of the second-order antiferromagnetic transition. For fields applied along the c axis, we observed a small but distinct anomaly at B^*, which we discuss in terms of a possible field-induced transition, probably weakly first-order. We further suggest that the transition corresponds to a change of magnetic structure. We revise magnetic phase diagrams of CeRhIn_5 for both principal orientations of the magnetic field based entirely on thermodynamic anomalies.
doi:10.1103/physrevb.103.045110 fatcat:e5rkllxavnejrbleyfw434mb3e