Anisotropic magnetic field responses of ferroelectric polarization in a trigonal multiferroic CuFe1-xAlxO2 (x=0.015)

TL;DR

This study explores how magnetic fields influence ferroelectric polarization in a trigonal multiferroic CuFe1-xAlxO2, revealing anisotropic responses linked to magnetic domain structures through neutron diffraction and other measurements.

Contribution

It provides the first detailed magnetic phase diagrams for CuFe1-xAlxO2 under various magnetic field directions, highlighting the anisotropic effects on ferroelectric helimagnetic order.

Findings

Established magnetic phase diagrams for three principal field directions.

Discovered anisotropic magnetic field dependence of ferroelectric order.

Linked magnetic domain structures to polarization responses.

Abstract

We have investigated magnetic field dependences of a ferroelectric incommensurate-helimagnetic order in a trigonal magneto-electric (ME) multiferroic CuFe1-xAlxO2 with x=0.015, which exhibits the ferroelectric phase as a ground state, by means of neutron diffraction, magnetization and dielectric polarization measurements under magnetic fields applied along various directions. From the present results, we have established the H-T magnetic phase diagrams for the three principal directions of magnetic fields; (i) parallel to the c axis, (ii) parallel to the helical axis, and (iii) perpendicular to the c and the helical axes. While the previous dielectric polarization (P) measurements on CuFe1-xGaxO2 with x=0.035 have demonstrated that the magnetic field dependence of the `magnetic domain structure' results in distinct magnetic field responses of P [S. Seki et al., Phys. Rev. Lett., 103 237601 (2009)], the present study have revealed that the anisotropic magnetic field dependence of the ferroelectric helimagnetic order `in each magnetic domain' can be also a source of a variety of magnetic field responses of P in CuFe1-xAxO2 systems (A=Al, Ga).