The role of harmonics in the first order antiferromagnetic to paramagnetic transition in chromium

Abstract

The results of Rice (see abstr. A13376 of 1971) and Malaspinas and Rice (see abstr. A1642 of 1972) on the effects of imperfect Fermi surface nesting in chromium are discussed to find the conditions under which imperfect Fermi surface nesting might give a first order antiferromagnetic-paramagnetic phase transition. These conditions are found to be not conducive to a stable antiferromagnetic state. A new mechanism for such a first order transition is proposed based on the existence of harmonics of the spin density wave. In this theory the transition is predicted to be always second order when T_N approaches zero. Since Kimball and Falicov (see abstr. A31753 of 1968) found the same result in their model it is likely that the authors' mechanism for a first order transition is the same as theirs. The presence of impurities is shown to reduce the tendency for a first order transition for alloys of chromium.