Spin correlations in the triangular-lattice random mixed antiferromagnet

Spin-glass-like freezing in the triangular-lattice random mixed antiferromagnet YFeMnO4 has been analysed by Monte Carlo simulation. Experimental results on random diluted LuGaMnO4 have also been presented. The analysis provides a qualitative interpretation of the experimentally observed spin freezing in the random mixed system YFeMnO4 as well as the diluted systems LuGaMnO4 and LuFeMgO4. The non-uniform antiferromagnetic interaction due to the random distribution of Mn2+ and Fe3+ in YFeMnO4 prevents long-range spin ordering, but instead it causes well-defined short-range correlation and a distribution of the relaxation time. The simulation demonstrates the formation of a higher-order structure of the short-range correlation at low temperatures. The development of a long-range correlation of quasi-static spins at the cusp temperature of the susceptibility is discussed.