Impurities in magnetic insulators studied by low-temperature nuclear orientation

Although the effects of impurities in metallic magnets have been extensively studied there have been far fewer experiments on impurities in insulating magnets, and, in an effort to understand this problem, we have investigated the effect of impurities in various systems. In MnCl2.4H(2)O samples doped with 1.6, 4.0 and 6.2% Co, the Mn-54 NMRON line is significantly broadened compared to the line in the pure crystal and shows structure on the low frequency side. The nuclear spin-lattice relaxation time is also lower by an order of magnitude. Mn-54 has also been doped into FeCl2.4H(2)O for which a 4-sublattice structure has been proposed and some details of this structure have been obtained.