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, ${\mathrm{La}}_{2-2x}{\mathrm{Sr}}_{1+2x}{\mathrm{Mn}}_2{\mathrm{O}}_7$ ( $x=0.3\mathrm{}$). 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 $\Delta {\rho }_c/{\rho }_c\sim 4000\%$ at 4.2 K under $\sim 10\mathrm{kbar}$.