Pressure effects in itinerant antiferromagnetism of Cr and its alloys

Abstract

Recent studies of pressure effects on the antiferromagnetism in Cr and its alloys are reviewed with emphasis, on the commensurate-incommensurate transition under pressure, the empirical relation between increasing pressure and decreasing electron to atom ratio for dilute alloys and its breakdown at higher concentrations, and the suppression of antiferromagnetism with pressure. The theory of the commensurate-incommensurate transition is discussed using a simplified model in which the relative sizes of the electron and hole pockets Vary. Attempts to include a realistic band structure will be discussed. In particular, the earlier suggestion that the behavior in the limit TN → 0 is controlled by a " cusp " type Kohn anomaly is supported by a theoretical study of static susceptibility as a function of wave vector for the Cr-group metals. Using pressure to suppress the commensurate phase it is found that the Neel temperature when plotted against electron to atom ratio shows a break in slope at pure Cr, in accord with theoretical predictions based on the " depairing " effects of impurity scattering.