Spin crossovers in Mott–Hubbard insulators at high pressures

Abstract The high-pressure induced phase transitions initiated by electronic transition in 3d ions from the high-spin (HS) to the low-spin (LS) state (HS-LS spin-crossover) are considered. Behavior of the system with d 6 electronic configuration is investigated in the ground state of zero temperature and critical pressure P c . Magnetic properties of the Mott–Hubbard insulator (Mg 1− x Fe x )O are studied in the vicinity of the quantum critical point ( T =0, P c ). At the critical pressure of spin crossover P c , the spin gap energy e S between HS and LS states is zero. The quantum spins fluctuations HS⇔LS do not require any energy, and the antiferromagnetism is destroyed in the quantum critical point by the first order transition.