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Transient Excitation of Nuclei in Ferromagnetic Metals

 

作者: M. Weger,   E. L. Hahn,   A. M. Portis,  

 

期刊: Journal of Applied Physics  (AIP Available online 1961)
卷期: Volume 32, issue 3  

页码: 124-125

 

ISSN:0021-8979

 

年代: 1961

 

DOI:10.1063/1.2000373

 

出版商: AIP

 

数据来源: AIP

 

摘要:

Free precession signals and spin echoes have been observed fromFe57,Co59, andNi61nuclei in finely divided multidomain iron,cobalt, and nickel, respectively. Spin-lattice relaxation has beenstudied in all three metals from temperatures in the liquid heliumrange to room temperature or above. Although the relaxation is notstrictly exponential, the rate of recovery of the magnetizationappears to be proportional to the absolute temperature. Spin-spinrelaxation has been studied in natural cobalt and in both naturaland enriched samples of iron and nickel. The spin-spin coupling isvery much stronger in cobalt than in iron or nickel, as expected,because of the very much larger nuclear magnetic moment ofCo59.Spin diffusion through the frequency spectrum of cobalt has beeninvestigated at 4.2 and 77°K by the stimulated echo technique.The results are consistent with a theory of one-dimensional diffusionwith exchange rate and exchange distance of the order of1/T2. The spin-echo technique has also been used in all threemetals to study the effect of domain wall motion on the nuclearresonance. A dc pulse, which displaces the domain walls by acontrollable amount, is placed between the first rf pulse and theecho. This study confirms that the induction signals arise fromnuclei in domain walls and further suggests a connection betweenline broadening and domain wall processes. A weak free-precessionsignal, arising from domain rotation, has been observed fromcobalt in high magnetic fields. The sign of the precession has beendetermined, confirming that the hyperfine field is directed oppositeto the magnetization.

 

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