Magnetic phase transition and multiferroic phase separation in Ho1-xGdxMnO3

Abstract

In the orthorhombic (o) RMnO3 compound, it is known that the magnetic state can change from the A-type antiferromagnetic (A-AFM) through a spiral spin order (SSO) into the E-AFM state with the decrease in the R ionic radius (rR). The magnetic phase transition from the E-AFM state to the A-AFM state is expected, but no experimental realization has been reported. In this study, this process in o-Ho1-xGdxMnO3 (x: 0–0.6) is reported. A substitution of Ho with Gd enables the transition of the multiferroic ground state from the E-AFM order (at x ≤ 0.1) to the SSO (at x > 0.4). Accompanied by the quenched disorder, a multiferroic phase separation state is demonstrated in the intermediate composition range of 0.1 < x < 0.4 near the phase boundary between the E-AFM and SSO. This phase-separated state is believed to enhance the ferroelectric polarization and magnetoelectric coupling. Our results demonstrate the dependences of the multiferroic properties of RMnO3 on rR and confirm that the multiferroic phase separation is an effective approach to enhance the multiferroic properties of RMnO3.