Magnetization measurements of 0, 5, 10, and 20 at.% Al-substituted first-transition-series alloys

Precision measurements on saturation moments of Cr-Fe, Fe-Co, Fe-Ni, and Co-Ni alloys with 0, 5, 10, and 20 at. % Al substitutions are reported; they show linear decrease of the mean atomic moment M at low Al concentration c. The negative slopes -dM/dc vary with the electron to atom ratio z of the transition metal: They show a maximum near z similar or equal to 8.3, as does the Slater-Pauling curve, and decrease to -dM/dc similar or equal to 3.0 mu(B)/(Al atom) near pure nickel. At concentrations close to pure Fe, there is a sharp drop to -dM/dc = 2.2 mu(B)/(Al atom). The moment decrease due to the Al solute is found to be in qualitative accord with M = M-0(1-c) -c(V-n(s))mu(B), where -(V-n(s))mu(B) is the moment induced by an impurity atom with valence V in the surrounding transition matrix with free-electron density n(s). This law takes for Ni as a particular case the known form M = M-0-cV mu(B). In the (Fe-Cr)-Al series the observed magnetic behavior is correlated with electronic-specific-heat data and critical concentrations for appearance of ferromagnetism.