Tuning competing magnetic interactions with pressure in RMn2O5 multiferroics

Magnetoelectric properties displayed in multiferroics are generally associated with complex magnetic orders. This complexity often results in a delicate balance between several geometrically frustrated magnetic exchange interactions. Applying pressure will thus unbalance this equilibrium and strongly affect the multiferroic properties. In this paper, we study the effect of pressure on magnetism in three particular members of the RMn2O5 multiferroics (R = Gd, Sm, and Nd) with interesting magnetic orders. Using powder neutron diffraction, we studied the evolution of their magnetic structures as a function of pressure. Despite their singular properties with respect to the other compositions, we demonstrate that these three members present the same pressure-induced commensurate phase (PCM) with the propagation wave vector [q(PCM) = (1/2, 0, 1/2]. Furthermore, the stabilization of the PCM phase under pressure can be explained by a similar mechanism. We ultimately conclude that the different origin of the CM and PCM phases of these three compounds are related to the competition of only two superexchange interactions, namely J(1) and J(6).