Theory of the pressure dependence of a prototype exchange integral

Abstract

The variation of electron exchange integrals in solids subjected to hydrostatic pressures $P$ is considered by examining a prototype exchange integral $J$. The quantity $(\frac{1}{J})(\frac{\mathrm{dJ}}{\mathrm{dP}})$ is determined within the context of a theory of solids under hydrostatic pressures in which the application of pressure is represented in terms of the crystal compressibility and two parameters which are associated with electronic screening and wavefunction-distortion effects. Pressure variations of magnetic-phase boundaries, exchange-enhanced susceptibilities, and exchange interactions of pairs of ${\mathrm{Cr}}^{3+}$ ions in ruby are considered as examples of the applications of the results.