Complex incommensurate magnetic phases in multiferroic Co3TeO6
Chi-Hung Lee1*, Chin-Wei Wang2, Yang Zhao3, Jeffery W. Lynn3, Chih-Chieh Chou4, Hung-Duen Yang4, Helmuth Berger5, Wen-Hsien Li1
1Department of Physics, National Central University, Jhongli 32001, Taiwan
2Neutron Group, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
3NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg,Maryland 20899, USA
4Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
5Institute of Physics of Complex Matter, EPFL, Lausanne, Switzerland
* presenting author:Chi-Hung Lee,
Multiferroic is the term used to indicate the phenomenon where ferroelectricity and magnetic ordering coexist. Understanding the nature of this coupling between ferroelectricity and magnetic ordering is a primary motivation for investigating these materials both for fundamental purposes and to enable the tailoring of materials properties and designing devices with the necessary magnetoelectric (ME) coupling for spintronics applications. In this study, I focus on the observations and explanations of a strong interplay between the order parameters of ferroelectricity and magnetic order in cobalt tellurate Co3TeO6. Neutron diffraction, magnetic susceptibility, specific heat, and dielectric constant have all been measured to identify the complex magnetic phases. The dominant exchange interactions are identified by considering the geometrical arrangement of severely distorted CoO6 octahedra and CoO4 tetrahedra, which naturally divide into two different types of layers, one of which consists of zigzag chains. These zigzag chains are the first to develop magnetic order at TM1 = 26 K, which is incommensurate in nature. The other separate layer of Co spins develops simple antiferromagnetic order at TM2 = 19.5 K. Our results are consistent with the previous findings of a spontaneous polarization below TM3 = 18 K. Anomalous variation in the incommensurate wave vector appear below TM4 = 16 K. The commensurate order parameter is shown to have a small dependence on the applied electric field, whereas no such effect is found for the incommensurate ordering. Below TM3, the thermal expansion is negative, and it also exhibits anomalies at TM2 and TM4.

Keywords: Multiferroic, Magnetoelectric effect, Neutron diffraction