Effects of pressure on charge transport and magnetic properties of La1.32Sr1.68Mn2O7 layered manganite

We have studied the effects of hydrostatic pressure on the electrical transport and magnetic properties of La1.32Sr1.68Mn2O7 layered manganite up to 25 kbars. At ambient pressure, the compound exhibits a ferromagnetic transition accompanied by a metal-insulator transition (TMI1) at 118 K. Increasing pressure induces a second metal-insulator (TMI2) transition at a critical pressure of 6≤PC≤7 kbars in the temperature dependence of resistivity measurement. With further increase in pressure, both TMI1 and TMI2 shift to higher temperatures continuously, however, displaying a suppression in the amplitude of the peaks on the resistivity curves. We could not observe any transition corresponding to TMI2 in the temperature dependence of magnetization measurement under pressures up to 10 kbars. However, pressure reduces the magnetic moments at low temperatures and shifts the TC to higher temperatures at the same rate observed for TMI1. A large negative tunneling magnetoresistance was observed around TC due to the ap...