SUPPRESSION OF WEAK FERROMAGNETISM IN SMALL PARTICLES OF GD2CUO4

Gd2CuO4 particles were synthesized by sol-gel techniques in order to s tudy the effects of particle size d on the magnetic properties measure d by de magnetization and microwave absorption. Decreasing d reduced t he intensity and temperature of onset of weak ferromagnetism, which wa s not detected at all in 850 Angstrom particles. This finding is attri buted to the impossibility of Cu three-dimensional antiferromagnetic o rdering when d reaches a limit somewhat below the two-dimensional magn etic correlation length corresponding to bulk Gd2CuO4 at the Neel temp erature.