Pressure Dependence of the 100 K Spin-State Transition in LaCoO3

The pressure dependence of the 100 K spin-state transition in LaCoO 3 is investigated through magnetization measurement under pressures of up to 18.2 kbar. The energy gap, Δ, between the low-spin ground state and the excited magnetic state (intermediate spin) increases remarkably with increasing pressure. The linear part of the pressure dependence of Δ, which is dominant below 5 kbar, is interpreted consistently by the volume expansion due to the spin-state transition under ambient pressure. In the higher pressure region, a quadratic pressure dependence is dominant, which suggests a very steep volume dependence of the energy of the excited magnetic state under the highly compressed condition.