Effect of the Interatomic Exchange Interaction on the Magnetic Phase Transitions in Spin Crossover Systems under High-Pressure

The phase diagram of an antiferromagnet with the spin crossover from the high-spin to low-spin state with S = 0 with increasing external pressure has been calculated with regard to the pressure dependence of the exchange integral. The calculated results are compared with the experimental data on ferropericlase Fe _x Mg_{1 – x}O.