Pressure-induced polar phases in multiferroic delafossite CuFeO

Terada, Noriki*; Khalyavin, D. D.*; Manuel, P.*; Osakabe, Toyotaka  ; Radaelli, P. G.*; Kitazawa, Hideaki*

We have studied the pressure effect on the magnetic orderings in the strongly frustrated antiferromagnet CuFeO, by using neutron diffraction experiments under hydrostatic pressure. The main result is elucidation of the pressure-temperature magnetic phase diagram, consisting of the fourmagnetic phases including two polar ones. In particular, in the 3 GPa P 4 GPa pressure range, the ICM2 phase with the proper screw magnetic ordering stabilized. This polar phase is almost identical to the ferroelectric incommensurate (FEIC) phase induced by either a magnetic field or chemical doping. Furthermore, above 4 GPa, a new low-symmetry phase ICM3 is realized. This is unique for the family of delafossite multiferroics and implies an admixture of both cycloidal and proper screw spin configurations. The sequence of the observed magnetic phases with changing pressure might be attributed to pressure suppression of the monoclinic lattice distortions responsible for releasing the spin frustration in the system.