Broken parity and a chiral ground state in the frustrated magnet CdCr2O4

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American Physical Society
We present a model describing the lattice distortion and incommensurate magnetic order in the spinel CdCr2O4, a good realization of the Heisenberg 'pyrochlore' antiferromagnet. The magnetic frustration is relieved through the spin-Peierls distortion of the lattice involving a phonon doublet with odd parity. The distortion stabilizes a collinear magnetic order with the propagation wave vector q=2π(0,0,1). The lack of inversion symmetry makes the crystal structure chiral. The handedness is transferred to magnetic order by the relativistic spin-orbit coupling: the collinear state is twisted into a long spiral with the spins in the ac plane and q shifted to 2π(0,δ,1).
spin-orbit interactions, Heisenberg model, phonons, crystal structure, broken parity, chiral ground state, antiferromagnetic materials, cadmium compounds, lattice distortion, incommensurate magnetic order, Heisenberg pyrochlore antiferromagnet, magnetic frustration, spin-Peierls distortion, magnetic order, phonon doublet, chiral crystal structure, relativistic spin-orbit coupling, CdCr2O4
Physical Review B (Condensed Matter and Materials Physics) 1 Aug. 2006, vol.74, no.6, pp. 60405-1-4