NMR-STUDY OF REENTRANT SPIN-GLASS STATE IN NIMN ALLOYS

The temperature dependence of the average hyperfine field and the nuclear spin-lattice relaxation time T//1 of **5**5Mn on three different types (i equals I, II and III) of Mn atoms in NiMn alloys containing 10 and 15 at% Mn have been measured. In 15 at% Mn alloy, the average hyperfine field associated with Mn atoms having an antiparallel moment mu //I//I//I increases abruptly at 12 K, while those associated with Mn atoms having parallel moments mu //I and mu //I//I do not with decreasing temperature. On the other hand T//1** minus **1 of **5**5Mn of all three types of Mn atoms are largely enhanced at the same temperature, 12 K. This behavior was not observed in 10 at% Mn alloy. The effects observed in 15 at% Mn alloy are considered to be due to the freezing of the transverse component of the antiparallel moment mu //I//I//I due to the onset of the re-entrant spin-glass transition at 12 K.