Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal

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Science  06 Dec 1996:
Vol. 274, Issue 5293, pp. 1698-1701
DOI: 10.1126/science.274.5293.1698


The current-perpendicular-to-plane magnetoresistance (CPP-MR) has been investigated for the layered manganite, La2−2xSr1+2xMn2O7 (x = 0.3), which is composed of the ferromagnetic-metallic MnO2 bilayers separated by nonmagnetic insulating block layers. The CPP-MR is extremely large (104 percent at 50 kilo-oersted) at temperatures near above the three-dimensional ordering temperature (Tc ≈ 90 kelvin) because of the field-induced coherent motion between planes of the spin-polarized electrons. Below Tc, the interplane magnetic domain boundary on the insulating block layer serves as the charge-transport barrier, but it can be removed by a low saturation field, which gives rise to the low-field tunneling MR as large as 240 percent.