Nuclear Magnetic Resonance in Dilute Cu-Base Cu-Mn Alloys

Abstract

By studying the ${\mathrm{Cu}}^{63}$ nuclear magnetic resonance in a series of Cu-Mn alloys at room temperature and at 4, 8, and 12.8 MHz, we have estimated the long-range quadrupole interaction—in addition to the previously measured magnetic one—between copper nuclear spins and magnganese impurities. Comparing wipeout numbers at 4 MHz, this interaction is about six times greater than the electric interaction measured in CuZn by Rowland. Using the measured size of the magnetic interaction and the calculated Ruderman-Kittel interaction, an order-of-magnitude estimate of the impurity-impurity interaction has been made. Also ${\mathrm{Cu}}^{63}$ spin-lattice relaxation times have been measured as a function of dc field in a 10-ppm alloy at 1.3°K, using field cycling, and the field dependence indicates that the magnetic interaction is predominantly scalar exchange. Finally, Overhauser enhancement of the ${\mathrm{Cu}}^{63}$ nuclear resonance was produced in the 10-ppm alloy at 1.3°K by applying 30- and 50-MHz rf to the sample in dc fields between 0 and 10 G. Both the temperature and the dc field dependence of this effect are puzzling, but the magnitude of the rf field needed suggests that the spin-lattice relaxation time of the localized impurity moment is longer than ${10}^{-8\mathrm{}}$ sec at 1.3°K.