Magnetic correlations and the influence of atomic disorder in frustrated isosceles triangular lattice antiferromagnet CuMnO

Terada, Noriki*; Tsuchiya, Yoshinori*; Kitazawa, Hideaki*; Osakabe, Toyotaka  ; Metoki, Naoto   ; Igawa, Naoki   ; Oyama, Kenji*

We have studied the magnetic correlations of the isosceles triangular lattice antiferromagnet CuMnO. Above , the magnetic correlations are characterized by a two-dimensional (2D) short-range correlation. Below , the magnetic structures have been identified to be collinear with the magnetic moments almost parallel to the orbitals. The stacking sequence along the direction is changed from antiferromagnetic to ferromagnetic by atomic disorder. We find that the second-nearest-neighbor interlayer interaction plays an important role for the magnetic stacking along the axis. The magnetic excitation below is characterized by collective spin-wave excitation with an energy gap of 6 meV from the three-dimensional long-range magnetic order and by spin-liquid-like 2D excitation, indicated by specific heat.