Valence instability of cerium under pressure in the Kondo-like perovskite La0.1 Ce0.4 Sr0.5 Mn O3

The effects of hydrostatic pressure and magnetic field on the electrical resistance of the Kondo-like perovskite manganese oxide, La0.1 Ce0.4 Sr0.5 Mn O3 with a ferrimagnetic ground state, have been investigated up to 2.1 GPa and 9 T. In this compound, the Mn moments undergo a double exchange mediated ferromagnetic ordering at TC ∼280 K and there is a resistance maximum, Tmax at about 130 K, which is correlated with an antiferromagnetic ordering of cerium with respect to the Mn-sublattice moments. Under pressure, the Tmax shifts to lower temperatures at a rate of d Tmax dP=-162 K GPa and disappears at a critical pressure Pc ∼0.9 GPa. Further, the coefficient, m of -ln T term due to Kondo scattering decreases linearly with increase of pressure showing an inflection point in the vicinity of Pc. These results suggest that cerium undergoes a transition from Ce3+ state to a Ce4+ Ce3+ mixed valence state under pressure. In contrast to the pressure effect, the applied magnetic field shifts Tmax to higher temperatures, presumably due to enhanced ferromagnetic Mn moments.