Type-II multiferroism and linear magnetoelectric coupling in the honeycomb Fe4Ta2O9 antiferromagnet
Résumé
Among the numerous exotic phenomena exhibited by honeycomb antiferromagnets, linear magnetoelectricity in niobiates and tantalates of an A(4)M(2)O(9) formula has been attracting a lot of attention. The magnetic frustration, first exploited in alpha-Cr2O3 in the 1960s, can be tuned in the "429" compounds of which structures derive from corundum, by varying the 3d orbitals filling (from 3d(5) to 3d(7) as A goes from Mn2+ to Co2+) and/or the size of the d(0)M cation (Nb5+ or Ta5+). Fe4Ta2O9 illustrates the physics richness of these compounds, as it exhibits a rare combination of multiferroism and linear magnetoelectricity associated to different magnetic field dependences of the electrical polarization.