We report powder and single-crystal neutron diffraction measurements, combined with x-ray powder diffraction data, to unravel the complex magnetic phase diagram and exchange coupling in Co3TeO6. The magnetic structures of the various phases differ markedly from those proposed by Ivanov on the basis of only powder diffraction data. 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 antiferromagnetic order of Γ4 symmetry at zero wave vector at TM2 = 19.5 K. Our results are consistent with the previous findings of a spontaneous polarization below T M3 = 18 K. Our neutron powder diffraction data indicate that the increase in the single-crystal (600) Bragg peak is due to a relief of extinction rather than to magnetic effects associated with the observed anomalous variation in the incommensurate wave vector at 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. A symmetry analysis and comprehensive phase diagram are given.
|期刊||Physical Review B - Condensed Matter and Materials Physics|
|出版狀態||已出版 - 26 11月 2013|