Effect of volume changes on the electronic and magnetic transitions in Pr1-xSrxMnO3 manganites (x = 0.7 and 0.5)

A study is made into the influence of hydrostatic pressure up to 16 kbar on temperature dependences of electrical resistance in polycrystalline manganites Pr1-xSrxMnO3 manganites (x = 0.7 and 0.5). It is shown that electrical resistance of Pr0.7Sr0.3MnO3 compound decreases under pressure, and the temperature of transition from ferromagnetic metallic state to nonmagnetic nonmetallic one (Tc) increases under compression. At atmospheric pressure Pr0.5Sr0.5MnO3 compound experiences transitions from antiferromagnetic nonconducting state to ferromagnetic metallic state at a temperature of Tt = 150 K, then to paramagnetic state at Curie point of TC = 265 K. Pressure effect on Pr0.5Sr0.5MnO3 results in a Tc inconsiderable decrease and in an exponential increase of transition temperature Tt. It is established that under pressures above Pc = 20 kbar a ferromagnetic phase disappears at the expense of antiferromagnetic phase field widening. The disappearance of the ferromagnetic phase under pressure is associated with a decrease of a chemical bond angle between manganese cation layers in perovskite laminated structure and with corresponding weakening of positive double exchange