The magnetic disturbances associated with substitutional impurities in nickel

Abstract

The disturbances in magnetization around a wide variety of impurities in nickel (Zn, Al, Ga, Si, Ge, Sn, Sb, non-transition metals; Nb, Mo, Ru, Rh, 4d elements; W, Re, 5d elements) have been measured by the neutron diffuse scattering method. This work is an extension of an earlier study (by Collins and Low) of the 3d transition elements V, Cr, Mn, Fe dissolved in nickel. Two distinct kinds of magnetization distribution have been observed. In one category (Mn, Fe, Rh) the magnetic disturbance is positive and confined to the impurity site. The other solutes lead to a widespread negative magnetic disturbance extending some five angstroms into the nickel lattice. With the exception of V, the individual scattering curves of the second class approximately superpose, when normalized at a single point. This leads to the conclusion that the spatial form of the moment disturbance in the nickel matrix is similar for Zn, Al, Ga, Si, Ge, Sn, Sb, Nb, Cr, Mo, Ru, W and Re and suggests that this wide variety of impurities affects the nickel matrix through the same mechanism. Differences between the impurities show up in the strength of the disturbances. In discussing the nature of these magnetic defects, a molecular field theory model is used to illustrate a possible mechanism for linking the spatially widespread losses of moment with a more localized driving force. A transition element solute gives rise to a widespread negative defect or to a positive disturbance confined to the solute site depending on whether or not formation takes place of the bound impurity states proposed by Friedel.