NUCLEAR MAGNETIC RESONANCE STUDY OF A COPPER NIOBIUM SUPERLATTICE (LAYERED ULTRATHIN COHERENT STRUCTURE) (NMR, COMPOSITIONALLY MODULATED ALLOY).

摘要

We have performed a nuclear magnetic resonance study of a Cu/Nb superlattice. NMR was performed on both isotopes of the Cu nuclei, with the superlattices both on and off the substrates on which they were deposited. The Cu was found to be divided into electronically distinct regions. The first, called bulk-Cu, had NMR properties similar to ordinary copper, with two exceptions: a 20% to 40% shorter spin-lattice relaxation time, and a possible anisotropic Knight shift. The bulk-Cu region comprised 19% of the copper nuclei in the superlattice. The other region, called shifted-Cu, comprised 63% of the copper nuclei. They experienced a large, isotropic, negative frequency shift, and some an anisotropic shift as well. The spin-lattice relaxation times for shifted-Cu nuclei were one to two orders of magnitude longer than that in ordinary copper.