High hydrostatic pressure effect on magnetic state of anion-deficient La0.70Sr0.30MnOx perovskite manganites

The magnetic state of La0.70Sr0.30MnOx (x = 2.85, 2.80) anion-deficient manganites is studied experimentally under hydrostatic pressure up to 5.2 GPa. These materials possessing the properties of a spin-glass state. The La0.70Sr0.30MnO2.85 exhibits a coexistence of the rhombohedral (R (3) over barc) and tetragonal (I4/mcm) crystal structures and below T-f similar to 50 K the spin-glass state is formed. The La0.70Sr0.30MnO2.80 exhibits the tetragonal (I4/mcm) crystal structure. For this compound a phase-separated magnetic state below Tf is formed, involving coexistence of C-type antiferromagnetic (AFM) clusters within spin-glass matrix. In both compounds the crystal structure and magnetic states remain stable upon compression. Under the hydrostatic pressure up to 1 GPa, the La0.70Sr0.30MnO2.85 is a spin glass with a smeared phase transition to the paramagnetic state. The freezing temperature T-f of the magnetic moments of the ferromagnetic clusters increases at a rate of 4.30 K/GPa and the magnetic ordering temperature T-MO increases at a rate of 12.90 K/GPa. The enhancement of the ferromagnetic properties of La0.70Sr0.30MnO2.85 anion-de. ficient manganite under hydrostatic pressure is explained by the redistribution of oxygen vacancies and a decrease in the unit cell parameters. (c) 2008 Elsevier B.V. All rights reserved.