Tuning competing magnetic interactions with pressure in RMn2O5 multiferroics

Abstract

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 (qPCM = ( 1 2 , 0, 1 2 )). Furthermore, the stabilization of the PCM phase under pressure can be explained by similar mechanism. We ultimately conclude that the different origin of the CM and PCM phase of these three compounds are related to the competition of only two super-exchange interactions, namely J1 and J6.

Dimer Physics in the Frustrated Cairo Pentagonal Antiferromagnet Bi2Fe4O9

“…Below T N , the long-range magnetic order is finally triggered by the weakest J 2 interaction, connecting the pentagonal planes. Note that Bi 2 Fe 4 O 9 is not the unique materialization of the Cairo lattice as it is related to a wide family of compounds including the multiferroic RMn 2 O 5 (R a rare-earth/Y, Mn occupying the pentagonal lattice) whose complex magnetodielectric phase diagrams could be investigated in the renewed perspective of pentagonal physics [26,38,39].…”

Infrared phonon spectroscopy on the Cairo pentagonal antiferromagnet Bi2Fe4O9: a study through the pressure induced structural transition

“…Indeed, the change in the J 4 interaction as well as the possibility of new exchange paths can release the frustration at the origin of the peculiar 90 • magnetic structure. Modifications in the magnetic structure under pressure have actually been observed in related compounds of the RMn 2 O 5 family with R a rare-earth atom 43,44 . They crystallize in the same space group, forming pentagons of Mn 3+ and Mn 4+ , where the Mn tetrahedra are connected by two oxygens instead of one as in Bi 2 Fe 4 O 9 .…”