Studies on magnetic field and temperature driven magneto-structural phase transition in La0.5Sr0.5MnO3+δ

The influence of magnetic field on the crystal structure of colossal magnetoresistance (CMR) material La0.5Sr0.5MnO3+δ has been investigated. Low temperature high-magnetic field powder X-ray diffraction (XRD) measurements were carried out on La0.5Sr0.5MnO3+δ in temperature range from 4.2 to 300 K and magnetic field range from 0 to 8 T. A first order structural phase transition from tetragonal I4/mcm to orthorhombic Fmmm phase, coupled with reported electronic and magnetic phase transition from ferromagnetic metal to antiferromagnetic insulator state has been started at ∼200 K and completed at ∼100 K. On the application of 8 T magnetic field this magneto-structural phase transition shifted to lower temperature (∼162 K) with phase coexistence regime down to 4.2 K. Isothermal X-ray diffraction measurements at 150 K infer the evidence of magnetic field driven first order structural phase transition from Fmmm to I4/mcm. These results consistent with the resistivity and magnetoresistance results; present the microscopic evidence of strong spin-lattice coupling and reveal the magnetic field driven structural phase transition as the origin of observed colossal magnetoresistance in this material.