Nuclear Magnetic Resonance in Ferro- and Antiferromagnets

Magnetic properties of pure and Gd-doped EuO probed by NMR

“…20 In EuO the magnetic anisotropy is low and consequently the amplification factor for nuclei in domain walls is not substantially stronger than for nuclei in domains. Indeed, the amplification in domains is given by η Domain = |H hf |/|H an + H int |, where H hf is the hyperfine field, H an is the anisotropy field and H int is the internal field defined as the sum of the external field, the demagnetization field and the Lorentz field 21 .…”

Mn55NMR and magnetization studies ofLa0.67Sr0.33Sidorenko1, Allodi2, Renzi3 et al. 2006Phys. Rev. B283191View full textAdd to dashboardCite

“…Two mechanisms of enhancement may typically be distinguished in homogeneous ferromagnets. One is due to the rf-induced motion of the domain walls, 16,17 it is generally dominant in zero field and obviously removed by the application of a static field approaching the saturation value. The other mechanism, which is usually less effective by one-two orders of magnitude, arises from the rotation of the magnetization in the bulk of domains, and it comes into play both in zero and in an applied field.…”

“…16,17 Since the hyperfine field is huge for transition metal nuclei, this gives rise to a large amplification (enhancement) of the rf field at the nucleus, h = ηh 0 . The enhancement factor η may be directly assessed by experiment from the optimal radiofrequency pulse excitation, which implies that:…”

“…The corresponding domain enhancement factor can be related to the local field at the nucleus H n , and the effective magnetic anisotropy by a simple theoretical model. 16 Since H n is essentially the hyperfine field (i.e.…”

C59oNMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

“…Internal field 59 Co NMR of ferromagnetic Co was first observed in 1959 by Gossard and Portis,7 and since then the application of internal-field NMR to ferromagnetic materials has developed considerably. [8][9][10] There has been an extensive subsequent use of 59 Co NMR to characterize the different Co atomic environments ͓fcc, hcp, and sfs͔ in Co metal, [11][12][13][14][15] in Co films, [16][17][18][19] in catalysts, 20,21 and in alloys. [22][23][24][25][26] However, the allotropic phase transformation of small Co particles has never been investigated by NMR spectroscopy.…”