Resonant x-ray scattering studies of the magnetic structure near the surface of an antiferromagnet

Watson, G.M.; Gibbs, Doon; Lander, G. H.; Gaulin, B. D.; Berman, L. E.; Matzke, Hj.; Ellis, W. P.

doi:10.1103/physrevb.61.8966

Cited by 31 publications

(14 citation statements)

References 48 publications

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“…The fitted charge scattering factors shown in Fig. 3 are similar to those found in other uranium systems 24 and are in close agreement with self absorption corrected fluorescence data 12 . The magnetic-charge interference scattering has been used to determine the profile of the uranium magnetization.…”

Section: Discussionsupporting

confidence: 87%

“…The scattering factors of Fig. 3, determined from the fitted calculations of the charge scattering, are similar in shape and magnitude to those measured across the U M 4 edge in other uranium systems 24 . The good agreement between the fluorescence measurements, corrected for self absorption effects 12 , and the imaginary part of the resonant scattering factor, shown in Fig.…”

Section: Discussionsupporting

confidence: 64%

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Profile of the U5fmagnetization inU∕Femultilayers

et al. 2008

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Recent calculations, concerning the magnetism of uranium in the U/Fe multilayer system have described the spatial dependence of the 5f polarization that might be expected. We have used the x-ray resonant magnetic reflectivity technique to obtain the profile of the induced uranium magnetic moment for selected U/Fe multilayer samples. This study extends the use of x-ray magnetic scattering for induced moment systems to the 5f actinide metals. The spatial dependence of the U magnetization shows that the predominant fraction of the polarization is present at the interfacial boundaries, decaying rapidly towards the center of the uranium layer, in good agreement with predictions.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionsupporting

confidence: 64%

Profile of the U5fmagnetization inU∕Femultilayers

et al. 2008

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“…In the presence of this so-called surface-induced disorder, correlation lengths both parallel and perpendicular to the surface diverge at the bulk first-order transition point, thus inducing anisotropic power law behaviour for some bulk quantities [39]. A possible realization of this scenario may be encountered in the antiferromagnet UO 2 where the surface layers order continuously while the bulk displays a discontinuous ordering [40]. A second intriguing scenario is encountered in the q-state Potts model [41,42] where a phase transition to a low temperature phase with an ordered bulk but a disordered surface is observed.…”

Section: Surface Quantities and Phase Diagramsmentioning

confidence: 99%

Critical phenomena at perfect and non-perfect surfaces

Pleimling¹

2004

J. Phys. A: Math. Gen.

100

135

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Abstract. In the past perfect surfaces have been shown to yield a local critical behaviour that differs from the bulk critical behaviour. On the other hand surface defects, whether they are of natural origin or created artificially, are known to modify local quantities. It is therefore important to clarify whether these defects are relevant or irrelevant for the surface critical behaviour.The purpose of this review is two-fold. In the first part we summarise some of the important results on surface criticality at perfect surfaces. Special attention is thereby paid to new developments as for example the study of surface critical behaviour in systems with competing interactions or of surface critical dynamics. In the second part the effect of surface defects (presence of edges, steps, quenched randomness, lines of adatoms, regular geometric patterns) on local critical behaviour in semi-infinite systems and in thin films is discussed in detail. Whereas most of the defects commonly encountered are shown to be irrelevant, some notable exceptions are highlighted. It is shown furthermore that under certain circumstances non-universal local critical behaviour may be observed at surfaces.

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“…(3) REXS allowed the observation of scattering from the surface of the antiferromagnet UO 2 [9,10]. These experiments (at BNL) showed that a dead layer was formed at the surface of the crystal, probably due to a change in the stoichiometry, and that the first-order nature of the transition (AF to para) became 2 nd order at the surface, as expected from theory.…”

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confidence: 52%

Resonant elastic X-ray scattering from 5f systems

Lander

2012

Eur. Phys. J. Spec. Top.

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Abstract. The first REXS experiments on a uranium compound at the U M 4 edge (3.728 keV) took place at BNL twenty years ago. An enormous enhancement of the scattering intensity was found. Since that time many other systems have been examined. This paper reviews some of the highlights of resonant scattering from actinide systems, and attempts to extrapolate what might be the future of this field.Soon after resonant scattering was discovered at the L edges in Ho [1], it was realised that the strongest effects in resonant elastic X-ray scattering (REXS) could be observed if the transitions involve partially occupied shells with strongly spin-polarised states. Thus the largest resonant effects are found when the L 2,3 edges are used for transition metals of the 3d series, and at M 4,5 (or N 4,5 ) edges for the 4f and 5f series. In the case of the M 4,5 edges of the actinides (5f ) the energies are between 3.5 and 5 keV, so within reach of many diffractometers, without the complications of soft X-rays. Hence the first experiment on UAs [2] at BNL in 1989 found the resonant enhancement to be about 6 orders of magnitude.In the 20 years since this experiment a great many 5f systems have been examined. Some noteworthy highlights are briefly mentioned in this extended abstract.(1) Extension to transuranium materials. At BNL studies were done with NpAs to show both critical scattering and a full examination of the magnetic structure [3,4]. Later, after some difficulties with the crystal surfaces [5], experiments were successfully done on a series of (U 1−x Pu x )Sb single crystals [6,7]. This latter study found an interesting effect at the Pu M 5 edge [7], but this has not been confirmed by XMCD experiments, so its origin remains in doubt. (2) In Ref. [6,7] the element specific nature of REXS was well demonstrated. Another study at ID20 (ESRF) examined alloys of (U 1−x Np x )Ru 2 Si 2 , where the parent compound with x = 0 is the famous heavy-fermion "hidden-order" material, which is still not understood. In REXS study [8] scaling gave a magnetic moment of ∼0.4µ B on the U atom. This was attributed to the large molecular field provided by the ordered Np moments (of 1.5µ B ). It is now known that the large moment state of URu 2 Si 2 does indeed have a moment of this magnitude.

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Resonant x-ray scattering studies of the magnetic structure near the surface of an antiferromagnet

Cited by 31 publications

References 48 publications

Profile of the U5fmagnetization inU∕Femultilayers

Profile of the U5fmagnetization inU∕Femultilayers

Critical phenomena at perfect and non-perfect surfaces

Resonant elastic X-ray scattering from 5f systems

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