Pressure dependence of the magnetization in the itinerant electron model of ferromagnetism

Abstract

The pressure dependence of the magnetization delta zeta / delta p is calculated in the itinerant electron model of ferromagnetism. It is assumed that the relative population of s and d bands, the width of the d band W and the effective interaction I_eff vary with pressure. Under these assumptions, a general expression for delta zeta / delta p is obtained which is exact within the Stoner model. The two important parameters which govern the pressure dependence of the magnetization in this model are the s-d transfer under pressure dn/dp and the pressure dependence of the effective interaction delta I_eff/ delta W. The temperature dependence of delta zeta / delta p is evaluated numerically for a single parabolic band and the values of parameters appropriate to nickel. The calculated temperature dependence of delta zeta / delta p is compared with the experimental data of Tange and Tokunaga (1969). Good quantitative agreement is obtained in the whole range of temperatures if the following values of the parameters dn/dp and delta I_eff/ delta W are chosen: dn/dp=-1.62*10^-7 bar^-1, delta I_eff/ delta W=8.68*10^-2. From the pressure dependence of I_eff the correlation effects in nickel are estimated. It is found that the ratio I_eff/I₀=0.4+or-0.1, which implies an immediate correlation effect.