Spontaneous spin-lattice coupling in the geometrically frustrated triangular lattice antiferromagnet CuFeO2 (original) (raw)

We use high-resolution synchrotron x-ray and neutron diffraction to study the geometrically frustrated triangular lattice antiferromagnet CuFeO 2. On cooling from room temperature, CuFeO 2 undergoes two antiferromagnetic phase transitions with incommensurate and commensurate magnetic order at T N1 = 14 K and T N2 = 11 K, respectively. The occurrence of these two magnetic transitions is accompanied by second-and first-order structural phase transitions from hexagonal to monoclinic symmetry. Application of a 6.9 T magnetic field lowers both transition temperatures by ϳ1 K, and induces an additional incommensurate structural modulation in the temperature region where the field-driven ferroelectricity occurs. These results suggest that a strong magneto-elastic coupling is intimately related to the multiferroic effect.