Spin-State Transition in La1-xPrxCoO3

We have investigated the crystalline structure and the magnetic properties of La 1- x Pr x CoO 3 single crystals. The crystalline symmetry is rhombohedral R \bar3 c for 0 ≤ x ≤0.3, and orthorhombic P n m a for 0.7 ≤ x ≤1. The lattice volume decreases monotonically with increasing Pr content due to the smaller ionic radius of Pr 3+ than La 3+ . The temperature dependence of the magnetic susceptibility [χ( T )] arising from Co 3+ ions in La 1- x Pr x CoO 3 was evaluated using La 1- x Pr x AlO 3 as a reference. The temperature dependence of the effective magnetic moment arising from Co ions is interpreted by the three spin-states low-spin (LS), intermediate-spin (IS) and high-spin (HS). The energy of the IS-state (Δ 1 ) increases with increasing Pr content through the chemical pressure. The chemical pressure dependence of Δ 1 agrees with the hydrostatic pressure dependence. In contrast to the first spin-state transition, the second spin-state transition is almost independent of the Pr content.