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arXiv · 0704.3566

Biquadratic antisymmetric exchange and the magnetic phase diagram of magnetoelectric CuFeO$_2$

M. L. Plumer
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Abstract

Biquadratic {\it antisymmetric} exchange terms of the form $ - [C_{ij} e^α_{ij}({\bf s}_i\times{\bf s}_j)_z]^2$, where ${\bf e}_{ij}$ is the unit vector connecting sites $i$ and $j$ and $α= x,y$, due partially to magnetoelectric coupling effects, are shown to be responsible for the spin-flop helical phase in CuFeO$_2$ at low magnetic field and temperature. Usual biquadratic {\it symmetric} exchange, likely due to magnetoelastic coupling, is found to support the stability of axial magnetic states at higher fields in this nearly-Heisenberg like stacked triangular antiferromagnet. A model Hamiltonian which also includes substantial interplane and higher-neighbor intraplane exchange interactions, reproduces the unique series of observed commensurate and incommensurate periodicity phases with increasing applied magnetic field in this highly frustrated system. The magnetic field-temperature phase diagram is discussed in terms of a Landau-type free energy.

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M. L. Plumer. 2007-07-04. Biquadratic antisymmetric exchange and the magnetic phase diagram of magnetoelectric CuFeO$_2$. https://doi.org/10.1103/physrevb.76.144411

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