Magnetotunneling in sputtered La0.7Ca0.3MnO3/Al2O3 multilayers

Magnetic multilayers in the form of [La0.7Ca0.3MnO3/Al2O3]n+La0.7Ca0.3MnO3 were sputtered to study their magnetotunneling effect. Structural analyses were performed by standard x-ray scattering, showing a well-defined superlattice. Both current perpendicular to plane (CPP) and current in plane (CIP) methods were applied for the magnetoresistance measurements. The CPP value gives the tunneling effect through the thin insulating layers and shows a large low-field effect of about 60% for the trilayer junction and 50% for the superlattice structure at 5 K, respectively. The CIP effect is about 30% (5 K) for all samples and is dominated here by the contribution of the intergrain tunneling effect within the La0.7Ca0.3MnO3 layers.