Pressure-Enhanced Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal
The pressure-induced variations of the anisotropic charge-transport and magnetic properties have been investigated for a bilayered manganite crystal, La{sub 2{minus}2x} Sr{sub 1+2x} Mn{sub 2}O {sub 7} (x=0.3 ). The magnitude of the magnetic coupling between the adjacent bilayers can be weakened by application of pressure, which makes the charge dynamics more two dimensional (2D) but highly incoherent. As a result, the restoration of the interlayer hopping of the spin-polarized carriers by application of magnetic field, namely the field-induced 2D-3D crossover, gives rise to an extremely high ratio of interplane tunneling magnetoresistance, say, up to {Delta}{rho}{sub c}/{rho}{sub c}{approximately}4 000{percent} at 4.2K under {approximately}10 kbar. {copyright} {ital 1997} {ital The American Physical Society}