Pressure effects on the magnetic structure in La 0.5Ca 0.5?xSr xMnO 3 (0.1≤x≥0.4) manganites

Abstract

The effect of high pressure (0-8 GPa) on the magnetic structure of polycrystalline samples of La 0.5Ca 0.5?xSr xMnO 3 (0.1≤x≥0.4) at 5 K is investigated using neutron-diffraction technique. Application of pressure is found to modify the previously reported magnetic structure, observed under ambient conditions, in these compounds. In x=0.1 composition, at 4.6(2) GPa and beyond, A -type antiferromagnetic structure is found to coexist with charge-exchange (CE)-type antiferromagnetic phase, observed at ambient pressure, with TN ∼150 K. For x=0.3 sample, as a function of pressure the CE-type phase is fully suppressed at 2.3(1) GPa and A -type antiferromagnetic phase is favored. Further Sr doping at x=0.4, the A -type antiferromagnetic phase is observed at ambient pressure and for T< TN (∼250 K). This phase is retained in the studied pressure range. However, the magnetic moment progressively reduces with increasing pressure, indicating the suppression of A -type antiferromagnetic phase. The present study brings out the fragile nature of the CE-type antiferromagnetic state in half-doped manganites as a function of pressure and disorder σ2. We observe that pressure required for destabilizing the CE-type antiferromagnetic state is reduced with increasing disorder σ2. External pressure and changing A -site ionic radii have analogous effect on the magnetic structure. © 2010 The American Physical Society.