Abstract
We have investigated the magnetic and electric ground states of a quasi-two-dimensional triangular lattice antiferromagnet (TLAF), , in which the effective spin of Co is 1/2. At zero field, the system undergoes a two-step transition upon cooling at K and K and enters a 120 ordered state. By applying magnetic fields, a series of spin states with fractions of the saturation magnetization are observed. They are spin states with 1/3, 1/2, 2/3 (or ) . The ferroelectricity emerges in all spin states, either with collinear or noncollinear spin structure, which makes another unique TLAF exhibiting both a series of magnetic phase transitions and multiferroicity. We discuss the role of quantum fluctuations and magnetic anisotropy in contributing more complex phase diagram compared to its sister multiferroic TLAF compound NiNb [J. Hwang et al., Phys. Rev. Lett. 109, 257205 (2012)].
4 More- Received 19 August 2013
- Revised 3 February 2014
DOI:https://doi.org/10.1103/PhysRevB.89.104420
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