Band Theory of Antiferromagnetism in 3d f.c.c. Transition Metals

The band structure of both paramagnetic and antiferromagnetic γMn is evaluated by G.F.M. with the Slater exchange approximation. The observed magnetic moment (2.3µ B ) is self-consistently obtainable, if the full Slater exchange is reduced by about one-half. The situation is the same at Cr. No special charactors are observed in E ( k )-curves of γMn contrary to the case of Cr. Introducing a simple exchange interaction term - J eff δ n 2 by the random phase approximation, we extend Mueller's interpolation scheme to apply to the antiferromegnetic case, and antiferromagnetism in f.c.c. structure is examined within the limit of the rigid band rigid band approximation. If we assume the value J eff =0.060Ry, f.c.c. Mn and f.c.c. Fe are antiferromagnetic and their magnetic moments are determined as 2.3µ B and 0.7µ B , respectively, which are in good agreement with experimental values. In f.c.c. structure the gap mechanism similar to Cr is found to be effective around N ≈7.3. The theoretical prediction seems to be supported by experiments of γFeMn alloy.