Magnetic-field-induced spin flop transition and magnetoelectric effect inCa2Fe2−xAlxO5

Abstract

Magnetic-field-induced spin flop transition and magnetoelectric effect in noncentrosymmetric ${\text{Ca}}_{2}$${\text{Fe}}_{2\ensuremath{-}x}$${\text{Al}}_{x}$${\text{O}}_{5}$ (0.5 $\ensuremath{\le}$ $x$ $\ensuremath{\le}$ 1) single crystals have been investigated. Temperature dependence of magnetic susceptibility shows that the compounds have antiferromagnetic transition temperatures ${T}_{N}$ above room temperature. The spin easy axis varies from the $c$ axis to the $a$ axis with increasing Al content $x$. When a magnetic field is applied along the spin easy axis, a spin flop transition takes place, accompanied by anomalies in the electric polarization and dielectric constant. The anomalies can be ascribed to a noncollinear spin arrangement in the domain walls between two magnetic phases and/or the spin direction dependent modulation of the metal-ligand hybridization. Such a polarization change with a spin flop transition in polar antiferromagnets may provide a route to realize large magnetoelectric coupling at high temperatures.