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m/sup +/SR studies on pure MnF/sub 2/ and site-diluted (Mn/sub 0. 5/Zn/sub 0. 5/)F/sub 2/

Description: Positive muon spin rotation and relaxation measurements have been carried out on the antiferromagnets, pure MnF/sub 2/ and site-diluted (Mn/sub 0.5/Zn/sub 0.5/)F/sub 2/, above and below the Neel temperature T/sub N/ using single-crystal specimens. Two different muon signals have been found in the pure MnF/sub 2/; with the precession frequency nu/sub A/ = 1.3 GHz for the site A and nu/sub B/ = 152 MHz for the site B measured in zero external magnetic field at T = 5 K. We propose a picture that the signal from the A site represents the ''muonium'' state, and discuss the characteristic features of muonium in magnetic materials. The spin relaxation rate 1/T/sub 1/, measured in zero external field, decreases rapidly with decreasing temperature below T/sub N/. The mechanism of the spin relaxation above T/sub N/ is explained by the exchange fluctuations of the Mn moments, while below T/sub N/ by the Raman scattering of spin waves. At the same normalized temperature T/T/sub N/, 1/T/sub 1/ observed in the diluted (Mn/sub 0.5/Zn/sub 0.5/)F/sub 2/ is significantly larger than that in the pure MnF/sub 2/ below T/sub N/. The difference between the pure and diluted systems is related to the large spectral weight of low-energy magnons in (Mn/sub 0.5/Zn/sub 0.5/)F/sub 2/ found by neutron scattering.
Date: January 1, 1986
Creator: Uemura, Y.J.; Keitel, R.; Senba, M.; Kiefl, R.F.; Kreitzman, S.R.; Noakes, D.R. et al.
Partner: UNT Libraries Government Documents Department

Determination of very slow. mu. /sup +/ hop rates in Cu by LLF-. mu. SR

Description: Muon spin relaxation in low (weak) longitudinal magnetic field (LLF-..mu..SR) provides a means of independently determining the static dipolar width ..delta.. characterizing the ..mu../sup +/ lattice site and the correlation time tau/sub c/ for ..mu../sup +/ hopping, in a manner that is nearly model-independent for tau/sub c/ and especially accurate in the near-static limit (tau/sub c/ > tau/sub ..mu../). The advantages of this method are illustrated by its application to muon hopping in Cu near the tau/sub c/ maximum around 50/sup 0/K.
Date: January 1, 1986
Creator: Brewer, J.H.; Celio, M.; Harshman, D.R.; Keitel, R.; Kreitzman, S.R.; Luke, G.M. et al.
Partner: UNT Libraries Government Documents Department

Application of muon spin relaxation experiment to the vortex dynamics of high temperature superconductors

Description: We discuss the potential use of muon spin relaxation ({mu}SR) technique to investigate the dynamics of the magnetic flux lines (vortices) in the mixed state superconductors. We agree that with the high critical temperature and large anisotropy found in some high temperature superconductors, one can use {mu}SR to observe both static and dynamic behaviors of vortices. Recent experiments on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} are interpreted in this context. 7 refs.
Date: January 1, 1991
Creator: Inui, M. (Los Alamos National Lab., NM (USA)) & Harshman, D.R. (AT and T Bell Labs., Murray Hill, NJ (USA))
Partner: UNT Libraries Government Documents Department

Application of muon spin relaxation experiment to the mixed state superconductors

Description: We discuss the use of muon spin relaxation ({mu}{sup +}SR) technique to study the mixed state of superconductors. Besides the application for static vortex configurations, we argue that large vortex motion can manifest itself as a narrowed time-averaged field distribution, which in turn results in a smaller relaxation rate. A static but disordered vortex configuration can also reduce the relaxation. We summarize these arguments. 7 refs.
Date: May 9, 1991
Creator: Inui, M. (Los Alamos National Lab., NM (USA)) & Harshman, D.R. (AT and T Bell Labs., Murray Hill, NJ (USA))
Partner: UNT Libraries Government Documents Department

Muon spin relaxation in ErRh/sub 4/B/sub 4/

Description: We have found that the erbium magnetic moment is so large that in ErRh/sub 4/B/sub 4/ it can relax muon polarization in times shorter than can be resolved by a typical ..mu..SR apparatus. The complete relaxation signal is resolved at temperatures above 50K only because of rapid fluctuation of the erbium moment, which partially decouples it from the muon's moment. Not much signal is resolved at temperatures less than or equal to 10K, but no dramatic effect is seen in crossing the superconducting transition temperature. The higher temperature local field fluctuation rates observed appear consistent with the exchange and spin-lattice fluctuation rates to be expected of erbium in this material. Perhaps more information on moment dynamics below 10K can be obtained by alloying erbium with a nonmagnetic rare earth such as yttrium within the RERh/sub 4/B/sub 4/ structure (as has been attempted for holmium), to reduce the rms local field at the muon.
Date: January 1, 1984
Creator: Noakes, D.R.; Ansaldo, E.J.; Brewer, J.H.; Harshman, D.R.; Huang, C.Y.; Torikachili, M.S. et al.
Partner: UNT Libraries Government Documents Department