Partially Disordered Phase in Frustrated Triangular Lattice Antiferromagnet CuFeO₂

抄録

We reinvestigated successive magnetic phase transitions (T_N1-- 14.0K, T_N2-- 10.5K) in a frustrated triangular lattice antiferromagnet (TLA) CuFeO₂ 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 Fe³⁺ magnetic ions.