We have studied the magnetic correlations of the isosceles triangular lattice antiferromagnet Cu1+xMn1-xO2 with x=0.00 and 0.04, using the magnetic susceptibility, specific heat, elastic, and inelastic neutron-scattering experiments. Above TN, the magnetic correlations in both samples are characterized by a two-dimensional (2D) short-range correlation, as indicated by the broad peak in the susceptibility and the asymmetric diffuse scattering observed in neutron diffraction experiments. Below TN, the magnetic structures, with the propagation vectors Q=(12̄1212) in x=0.00 and Q=(12̄120) in x=0.04, have been identified to be collinear magnetic structures with the magnetic moments almost parallel to the dz2 orbitals. Although the atomic disorder does not affect the direction and length of the magnetic moments in CuMnO2, the stacking sequence along the c direction is changed from antiferromagnetic to ferromagnetic. Considering the interlayer exchange interactions between isosceles triangular lattice layers, we find that the second-nearest-neighbor interlayer interaction plays an important role for the magnetic stacking along the c axis. The magnetic excitation below TN 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, as indicated by C(T) T2 in CuMnO2.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2011 Aug 26|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics