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Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal
1T. Kimura, Y. Tomioka, H. Kuwahara, A. Asamitsu, M. Tamura, Joint Research Center for Atom Technology (JRCAT), Tsukuba, 305, Japan. Y. Tokura, JRCAT, Tsukuba, 305, Japan, and Department of Applied Physics, University of Tokyo, Tokyo 113, Japan.
Abstract:
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 (10(4) percent at 50 kilo-oersted) at temperatures near above the three-dimensional ordering temperature (Tc approximately 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.