NMR study of re-entrant spin-glass state in NiMn alloys

Abstract

The temperature dependence of the average hyperfine field H̄ i and the nuclear spin-lattice relaxation time T 1 of 55Mn on three different types ( i = I, II and III) of Mn atoms in NiMn alloys containing 10 and 15 at % Mn have been measured. In 15 at % Mn alloy, H̄ III associated with Mn atoms having an antiparallel moment μ III increases abruptly at 12K, while H̄ I and H̄ II associated with Mn atoms having parallel moments μ I and μ II do not with decreasing temperature. On the other hand T −1 1 of 55Mn 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. These effects observed in 15 at % Mn alloy are considered to be due to the freezing of the transverse component of the antiparallel moment μ III due to the onset of the re-entrant spin-glass transition at 12 K.