Paramagnetic impurities in an itinerant antiferromagnet. Theory

Abstract

The effects of 3-d paramagnetic impurities in an itinerant antiferromagnetic metal are investigated using the Wolff–Clogston model. The changes in the Néel temperature TN, the energy-gap parameter, and the density of states are evaluated in the Hartree–Fock approximation and in the lowest order in the impurity concentration. The results on the changes in TN are compared with the experimental findings on V, Mn, Fe, Co, Ni, Mo, and W impurities in chromium. The agreement between theory and experiment suggests that the changes in TN are essentially due to three mechanisms: (a) the effect due to changes in the electron–atom ratio, (b) the spin-dependent scattering due to paramagnetic impurities, and (c) the changes in the intra-atomic coulomb potential at the impurity site. In the case of Mo and W, the last effect explains the observed decrease in TN in Cr.