Partially Disordered Phase in Frustrated Triangular Lattice Antiferromagnet CuFeO_<b>2</b>

Abstract

We reinvestigated successive magnetic phase transitions ( T N1 ∼14.0 K, T N2 ∼10.5 K) in a frustrated triangular lattice antiferromagnet (TLA) CuFeO 2 by neutron diffraction measurements using single crystals. The magnetic structure of the intermediate-temperature phase between T N1 and T N2 is found to be a quasi -long range ordered sinusoidally amplitude-modulated structure with a temperature dependent propagation wave vector ( q q 0). These features of successive phase transitions are well explained by reinvestigated Monte-Carlo simulation of a 2D Ising TLA with competing exchange interactions up to 3rd neighbors, in spite of the Heisenberg spin character of orbital singlet Fe 3+ magnetic ions.