Effect of high pressure on the crystal structure, magnetic, and vibrational properties of multiferroic RbFe(MoO4)(2)

The structural, magnetic, and vibrational properties of RbFe(MoO4) 2 have been studied by means of x-ray and neutron powder diffraction, magnetic susceptibility measurements, and Raman spectroscopy at pressures up to 10 GPa. The gradual structural phase transition from the initial trigonal P (3) over bar m1 phase to the monoclinic C2/c phase via the intermediate P (3) over bar phase was observed at P similar to 1 GPa. The triangular antiferromagnetic order with a propagation vector q = (1/3, 1/3, q(z)) in the suppressed trigonal phase remains incommensurate, and the q(z) value increases from 0.45 to 0.48 in the pressure range 0- 2 GPa at T = 2 K. The pressure coefficient of the Neel temperature is equal to (1/T-N)dT(N)/dP = 0.09 GPa(-1). No evidence of the formation of the long-range magnetic order in the monoclinic phase was found. The pressure dependencies of the vibrational modes for the trigonal and monoclinic phases were obtained.