Thermodynamics of the dipole-octupole pyrochlore magnet Ce₂Hf₂O₇ in applied magnetic fields

The recently discovered dipole-octupole pyrochlore magnet Ce₂Hf₂O₇ is a promising three-dimensional quantum spin liquid candidate which shows no signs of ordering at low temperature. Here we investigate the thermodynamic response to magnetic fields applied along the global [110] direction using specific heat measurements and fits using numerical methods, and solve the corresponding magnetic structure using neutron diffraction. Specific heat data in moderate fields are reproduced well, however, at high fields the agreement is not satisfactory. We especially observe a two-step release of entropy, a finding that demands a review of both theory and experiment. We address it within the framework of three possible scenarios, including an analysis of the crystal field Hamiltonian not restricted to the two-dimensional single-ion doublet subspace. We conclusively rule out two of these scenarios and find qualitative agreement with a simple model of field misalignment with respect to the crystalline direction. As a result, we discuss the implications of our findings for [111] applied fields and for future experiments on Ce₂Hf₂O₇ and its sister compounds.. Authors: Bhardwaj, Anish [Florida State University, Tallahassee, FL (United States); National High Magnetic Field Laboratory, Tallahassee, FL (United States); St. Bonaventure University, NY (United States)]; Porée, Victor [Paul Scherrer Institut (PSI), Villigen (Switzerland); Synchrotron SOLEIL, Gif-sur-Yvette (France)] (ORCID:0000000310067105); Yan, Han [Rice University, Houston, TX (United States)]; Gauthier, Nicolas [Université de Sherbrooke, Quebec (Canada)] (ORCID:000000016147243X); Lhotel, Elsa [Universite Grenoble Alpes (France)]. DOE Contract: SC0025047. Subjects: 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Exact diagonalization; Frustrated magnetism; Magnetization measurements; Neutron diffraction; Pyrochlores; Quantum spin liquid; Specific heat measurements