Nuclear relaxation ofMn55in Ni-Mn alloys

Abstract

Nuclear relaxation times of $^{55}\mathrm{Mn}$ have been studied in a series of Ni-Mn alloys containing between 1.0- and 14.4-at.% Mn using spin-echo techniques. ${T}_{1}$ was measured at 77 \ifmmode^\circ\else\textdegree\fi{}K and in some cases at 4.2 \ifmmode^\circ\else\textdegree\fi{}K as a function of external magnetic field. In the 1.0-at.% alloy ${T}_{1}T$ increases from a value of 30 msec \ifmmode^\circ\else\textdegree\fi{}K in zero field to a value of about 90 msec \ifmmode^\circ\else\textdegree\fi{}K at 18 kG. At 18 kG, ${T}_{1}T$ is found to decrease with increasing Mn concentration to a value of about 11 msec \ifmmode^\circ\else\textdegree\fi{}K at 14.4-at.% Mn. Various contributions to the nuclear relaxation are evaluated both in the dilute Mn in Ni alloy and in the more concentrated alloy. In the dilute alloy, spin-wave-enhanced conduction-electron relaxation appears to be the dominant relaxation mechanism, while in the more concentrated alloys the orbital relaxation may be important.