Nuclear magnetic resonance in single crystals of the dilute magnetic alloys: CuFe, CuCo, and CuNi
Stakelon, Thomas Stanley
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https://hdl.handle.net/2142/30701
Description
Title
Nuclear magnetic resonance in single crystals of the dilute magnetic alloys: CuFe, CuCo, and CuNi
Author(s)
Stakelon, Thomas Stanley
Issue Date
1974
Director of Research (if dissertation) or Advisor (if thesis)
Slichter, C.P.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Nuclear magnetic resonance (NMR)
Single Crystals
satellite resonances
isotropic field
Language
en
Abstract
"Nuc1ear resonances were 0 bserved f rom CU63 nuc1""e1 1n t he f'1rst f ew shells around Fe, Co, and Ni impurities in single crystals of their respective dilute alloys with copper. The resonances from these nuclei, called
63
satellites, occur at fields shifted from the much more intense Cumain
resonance field when observed at a fixed frequency. Satellites were
observed previously in these alloys in powdered samples only. The importance
of these satellite resonances lies in the information they yield
about the electronic structure of the magnetic impurity. Heretofore, there
has been no detailed analysis since the identification of which satellite
arises from which shell of neighboring nuclei was not possible. Field
shifts of most observed satellites were sensitive to the orientation of the
static magnetic field with respect to the crystal axes. By studying the
resulting single crystal rotation patterns, we were able to identify the
crystal symmetry of the shells from which the satellites originate as well
as to measure in detail the strength of the interactions responsible for
the anisotropic field shifts.
This data yielded positive identification of satellite resonances from the following neighboring shells of nuclei around the 3-d transition element impurity: CuFe, second and third; CuCo, first and second, CuNi, first. Large anisotropic field shifts due to the magnetic hyperfine interaction were measured at copper nuclei in the first shell neighboring Co atoms in a CuCo single crystal. The size and asymmetry of the interaction indicates a
pseudodipolar contribution about twice the magnitude of the direct dipolar contribution from the impurity moment. Similar conclusions are drawn for the third neighbor shell around Fe atoms in CuFe.
The electric field gradient tensor was determined at nuclei in the first neighbor shells around the 3-d transition element atoms in CuCo and CuNi. For CuNi the EFG tensor components are \,iQ = 1.12 ± .02 MHz and TQ = .21 + .03. In CuCo, the direction of the maximum electric field gradient is perpendicular to the radial direction from the impurity. The EFG tensor components in the latter case are \,iQ = .377 + .014 MHz and llQ = .50 ± .08.
The isotropic field shifts due to the contact term of the magnetic hyperfine interaction was measured for satellites from the above and other shells of neighboring copper nuclei."
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