Magnetic phase diagram and thermodynamic study of CuB₂O₄

Numerous studies on copper metaborate (CuB₂O₄) in the parametric space of magnetic

field (H) and temperature (T) have indicated existence of unusually complicated

magnetic phase transitions. However, a comprehensive specific heat study was not

available for the construction of a more complete H-T phase diagram on this system

until now. The specific heat data reveal a previously elusive phase boundary in the

high field regime, which is key to a conceptual understanding the complicated phase

diagram of CuB₂O₄ in such a rather narrow phase space. We have constructed a more

complete magnetic phase diagram of CuB₂O₄ by the combination of the specific heat,

magnetic, and neutron scattering measurements on the same sample. Moreover, the

quantitative analysis of entropy elucidates the distinct magnetic orderings at Cu(1)

and Cu(2) sites in CuB₂O₄ resolving a long standing issue.