Mössbauer Effect in Nickel‐Rich Nickel‐Manganese Alloys

Abstract

Nickel-rich nickel-manganese alloys with manganese concentrations of 2, 4, and 16 at yo have been investigated at various temperatures by Mossbauer spectroscopy using Fe57 88 the probe nucleus. The sample with 16 atyo Mn concentration has been studied in detail for various heat treatments. For all heat treatments i t shows anomalous spectra consisting of an intense central line together with a magnetic structure, over a wide range of temperatures. Three different possibilities have been considered to account for the anomalous spectre. They are the co-existence of two phases corresponding t o long-range order and short-range order, the co-existence of nickel-rich and manganese-rich regions, and relaxation effects.

Induced ordering in electrodeposited nanocrystalline Ni–Mn alloys

“…52 The introduction of hydrogen reduces the average magnetic moment of the nickel atom, lowering the Curie temperature as well as the hyperfine interaction of the iron atom. The doublet arises due to the presence of a quadrupole splitting, thus indicating an asymmetry in the environment around the resonant Fe atoms 22 or the presence of a nonmagnetic impurity.…”

“…This perhaps suggests the presence of a small number of short-range ordered domains in a matrix of long-range order, in agreement with literature results on bulk samples. 22,53 Fe nuclei in these two phases experience different hyperfine fields and the corresponding Curie transitions are different. The T C of the short-range order phase is presumably below room temperature and could be determined only with low temperature Mössbauer studies.…”

57 Fe Mössbauer Lineshapes in Disordered Ni3/Mn

“…This may be due to the fact that in computing lineshapes, perfect randomness (complete disorder) has been assumed regarding the positions of Ni and Mn atoms in the alloys. The 16 atyo Mn-Ni alloy is relatively insensitive to heat treatment with respect to both the saturation magnetisation [ 2 ] as well as 57Fe Mossbauer spectra [7]. This is the concentration a t which the influence of atomic ordering just manifests 1151 on the magnetic properties.…”