TRANSIENT EXCITATION OF NUCLEI IN FERROMAGNETIC METALS
Free precession signals and spin echoes were observed from Fe/sup 57/, Co/sup 59/, and Ni/sup 61/ nuclei in finely divided mul tidomain iron, cobalt, and nickel, respectively. Spin-lattice relaxation was studied in all three metals from temperatures in the liquid helium range to room temperature or above. Although the relaxation is not strictly exponential, the rate of recovery of the magnetization appears to be proportional to the absolute temperature. Spin-spin relaxation was studied in natural cobalt and in both natural and enriched samples of iron and nickel. The spin-spin coupling is very much stronger in cobalt than in iron or nickel, as expected, because of the very much larger nuclear magnetic moment of Co/sup 59/. Spin diffusion through the frequency spectrum of cobalt was investigated at 4.2 and 77 deg K by the simulated echo technique. The results are consistent with a theory of onedimensional diffusion with exchange rate and exchange distance of the order of 1/T/sub 2/ The spin-echo technique was used in all three metals to study the effect of domain wall motion on the nuclear resonance. A dc pulse, which displaces the domain walls by a controllable amount, is placed between the first rf pulse and the echo. This study confirms that the induction signals arise from nuclei in domain walls and further suggests a connection between line broadening and domain wall processes. A weak free- precession signal, arising from domain rotation, was observed from cobalt in hdgh magnetic fields. The sign of the precession was determined, confirmdng that the hyperfine field is directed opposite to the magnetization. (auth)
- Research Organization:
- Univ. of California, Berkeley
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-15-014875
- OSTI ID:
- 4050368
- Journal Information:
- Journal of Applied Physics (U.S.), Vol. Vol: 32: No. 3, Suppl.; Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
COBALT 59
CURRENTS
DIFFUSION
ENRICHMENT
EXCITATION
FERROMAGNETIC MATERIALS
FREQUENCY
HYPERFINE STRUCTURE
INTERACTIONS
IRON 57
LATTICES
LOW TEMPERATURE
MAGNETIC FIELDS
MAGNETIC MOMENTS
MAGNETISM
METALS
MOTION
NICKEL 61
NUCLEI
PULSES
QUANTITATIVE ANALYSIS
RADIO WAVES
ROTATION
SIGNALS
SPECTRA
SPIN
TEMPERATURE
TRANSIENTS