Exchange interaction between electron subsystems in iron-based F.C.C. alloys doped by nitrogen or carbon

The effect of nitrogen and carbon on the electronic and magnetic properties of the iron-base Fe56Cr18Ni16Mn10 3d-alloy with f.c.c. lattice (austenite) is studied by means of the magnetic resonance. It is shown that the electron state density on the Fermi surface in the nitrogen austenite is one order of magnitude higher than that in the carbon one. Based on measurements of the temperature dependence of the g-factor the existence of superparamagnetic clusters is stated, the latter being obviously clusters of substitutional solutes. Signs and values of the exchange interaction between conduction electrons and other magnetic subsystems are obtained from the analysis of the temperature dependence of the paramagnetic susceptibilities. The exchange interaction between conduction electrons and isolated localised spins has antiferromagnetic character, while conduction electron—cluster interaction is ferromagnetic. The size of the clusters is markedly higher in the carbon austenite. This difference in structural homogeneity can be used for an explanation of the higher thermodynamic stability of the nitrogen austenite as compared to the carbon one.