SPIN CORRELATIONS IN THE TRIANGULAR-LATTICE RANDOM MIXED ANTIFERROMAGNET

Spin-glass-like freezing in the triangular-lattice random mixed antife rromagnet YFeMnO4 has been analysed by Monte Carlo simulation. Experim ental 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 t he diluted systems LuGaMnO4 and LuFeMgO4. The non-uniform antiferromag netic interaction due to the random distribution of Mn2+ and Fe3+ in Y FeMnO4 prevents long-range spin ordering, but instead it causes well-d efined short-range correlation and a distribution of the relaxation ti me. The simulation demonstrates the formation of a higher-order struct ure of the short-range correlation at low temperatures. The developmen t of a long-range correlation of quasi-static spins at the cusp temper ature of the susceptibility is discussed.