A pulsed NMR study of narrow domain walls in DyAl<sub>2</sub>
G J Bowden; J M Cadogan; K R Doolan; P J Martinson; J M Pope; G J Bowden; School of Phys., Univ. of New South Wales, Kensington, NSW, Australia; J M Cadogan; School of Phys., Univ. of New South Wales, Kensington, NSW, Australia; K R Doolan; School of Phys., Univ. of New South Wales, Kensington, NSW, Australia; P J Martinson; School of Phys., Univ. of New South Wales, Kensington, NSW, Australia; J M Pope; School of Phys., Univ. of New South Wales, Kensington, NSW, Australia
Журнал:
Journal of Physics F: Metal Physics
Дата:
1982-02-01
Аннотация:
The results of a pulsed NMR study of the <sup>27</sup>Al resonance in DyAl<sub>2</sub> are presented and discussed. Quadrupole oscillations in the height of the spin-echo versus pulse separation tau have been found. The oscillations have been used to show that the magnetic hyperfine field at the <sup>27</sup>Al nuclei makes an angle of about 14.5 degrees with respect to the (001) direction of easy magnetisation. This result is consistent with an NMR signal originating either from within a domain or close to the edge of a narrow domain wall. In addition, a classical analysis of a 90 degrees domain wall in DyAl<sub>2</sub> is presented and used to compute RF enhancement factors eta , both within domain walls. It is shown, for example, that for an enhancement factor eta =500 at a Dy site the ratio of the crystal-field anisotropy to exchange (K/W) is about -0.035. This ratio is approximately six times smaller than a single crystal estimate of about -0.195, thereby implying that the <sup>163</sup>Dy NMR signal originates from domain walls, moving in regions of defects and imperfections.
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