Effect of oxygen off-stoichiometry on coupled structural and magnetic phase-transitions in La0.15Sr0.85MnO3−δ (δ=0.02, 0.14)

Effect of oxygen off-stoichiometry on the structural and magnetic properties of La0.15Sr0.85MnO3−δ (δ=0.02, 0.14) has been studied employing low-temperature x-ray diffraction, calorimetry, electrical-transport and magnetization. The nearly stoichiometric composition under goes first order phase-transition from cubic to tetragonal P4/mmm at 238 K accompanied by magnetic and electrical phase-transitions. On the contrary the off-stoichiometric composition does not show any transition and remains cubic Pm-3m down to 80 K. Off-stoichiometry induced oxygen-vacancy seems to suppress the cooperative JT distortion and possibly stabilize a G-type antiferromagnetic phase with localized canted spins. Thus we demonstrate that controlling oxygen stoichiometry is a way of structure/property engineering in electron-doped-like manganites.