Surface and interface investigations using radioactive atoms

Potzger, К.; Weber, Alfons; Manzhur, Y.; Prandolini, M. J.; Bertschat, H. H.; Zeitz, W.‐D.; Dietrich, M.

doi:10.1002/pssc.200405433

Cited by 4 publications

(19 citation statements)

References 21 publications

(36 reference statements)

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“…The calculated trends agree with the measured data. For N = 5 and 6 the positive values are reported in [8], but we make the remark that the sign has not been measured but rather deduced from comparison to calculations for 4sp impurities; thus here we show the same values but also with different sign, according to our calculations. The Cd s moment is also shown, to demonstrate its proportionality to H hf .…”

Section: Discussionsupporting

confidence: 68%

“…In conclusion, using first-principles calculations we have interpreted the measured [8] coordination dependence of H hf in Cd impurities in Ni. Our results show a strong, nonlinear dependence on the coordination number N, in agreement with experiment.…”

Section: Discussionmentioning

confidence: 92%

“…Now the observed coordination dependence of H hf for Cd probe atoms can be understood. In figure 3, H hf (N) is shown, together with the experimental results [8] and the calculated results for Te probes. For Cd, H hf increases and changes sign for lower N as the spin-up antibonding s-d hybrids come lower in energy, because of the weaker s-d hybridization.…”

Section: Discussionmentioning

confidence: 99%

“…In a recent experimental publication [8], the coordination number dependence of H hf for Cd impurities in a Ni host was studied, by comparing data from Cd positioned on several Ni surfaces. The conclusion was that the H hf for Cd strongly depends on the coordination number.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 3.The calculated coordination number dependence of H hf of Cd (full line, full circles) and Te (dashed line) probe atoms on Ni surfaces. The triangles correspond to experimental values reported in[8]. The coordination number N depends on the surface and on the position as described in table 1.…”

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confidence: 99%

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Coordination dependence of hyperfine fields of 5sp impurities on Ni surfaces

Mavropoulos¹

2003

J. Phys.: Condens. Matter

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We present first-principles calculations of the magnetic hyperfine fields H hf of 5sp impurities on the (001), (111), and (110) surfaces of Ni. We examine the dependence of H hf on the coordination number by placing the impurity in the surfaces, on top of them at the adatom positions, and in the bulk. We find a strong coordination dependence of H hf , different and characteristic for each impurity. The behavior is explained in terms of the on-site s-p hybridization as the symmetry is reduced at the surface. Our results are in agreement with recent experimental findings. PACS numbers: 73.20.Hb,75.75.+a,73.20.Hb,76.60.Jx The understanding of the magnetic properties of solids on the atomic level is a challenge for experiment and theory. The magnetic hyperfine interaction of the electronic magnetization with the nuclear magnetic moment of an atom is such a property, and it is known to depend in turn on the properties of the atom as well as on the neighboring atomic environment. In particular, for impurities in the bulk of the ferromagnetic materials Fe, Co, Ni, the trends of magnetic hyperfine field H hf have been well understood and the experimental and theoretical results extend practically over the whole periodic table [1,2]. The relation of H hf to the local magnetic moment and to the atomic environment is not trivial. Therefore, for the interpretation of the trends, first-principles, all-electron methods have been extremely useful [2], since they can describe the charge density and magnetization near the atomic nucleus self-consistently. H hf measurements for probe atoms at interfaces or surfaces can also provide unique information on the local structure [3], especially in combination with relevant calculations [4,5,6].One of the modern powerful experimental techniques allowing the study of the hyperfine interaction of impurities at surfaces or interfaces is the perturbed angular correlation spectroscopy [7]. It has a high enough sensitivity that allows accurate measurements from highly diluted probe atoms (10 −4 − 10 −5 of a monolayer), so that these form practically isolated impurities. In a recent experimental publication [8], the coordination number dependence of H hf of Cd impurities in Ni host was studied, by comparing data from Cd positioned on several Ni surfaces. The conclusion was that the H hf of Cd strongly depends on the coordination number. Although this might be expected, since the magnetic moment of the Cd impurity is not intrinsic but rather induced by the environment, the data show neither a linear dependence nor an increase with the number N of Ni neighbors. On the contrary, H hf is measured to be strongest for N = 3, while as N is progressively increased H hf seems to change sign and has a parabolic behavior.In order to interpret this puzzling behavior, we have performed first-principles calculations for all 5sp and the early 6s impurities (Ag to Ba) on various Ni surfaces and in bulk Ni in a substitutional position. The impurity positions studied are given in Table I together with the co...

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Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Coordination dependence of hyperfine fields of 5sp impurities on Ni surfaces

Mavropoulos¹

2003

J. Phys.: Condens. Matter

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Magnetic nanostructures: radioactive probes and recent developments

Prandolini

2006

Rep. Prog. Phys.

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The miniaturization of magnetic sensors and storage devices down to the nano-scale leads to drastic changes in magnetic phenomena compared with the same devices with a larger size. Excited-nuclear-probe (radioactive probe) techniques are ideal for investigating these new magnetic nanostructures. By observing the magnetic hyperfine fields (and in some cases the electric-field-gradients (EFGs)) at the nuclei of radioactive probes, microscopic information about the magnetic environment of the probes is acquired. The magnetic hyperfine field is particularly sensitive to the s-spin polarization of the conduction electrons and to the orbital magnetic moment of the probe atom. Three methods of inserting radioactive probes into magnetic nanostructures are presented; neutron activation, recoil implantation and 'soft-landing', followed by descriptions of their application to selected examples. In some cases, these methods offer the simultaneous creation and observation of new magnetic materials at the atomic scale. This review focuses firstly on the induced magnetism in noble-metal spacer layers between either ferromagnetic (FM) or FM/antiferromagnetic (AFM) layers in a trilayer structure. Using the method of low-temperature nuclear orientation, the s-spin polarization of noble-metal probes was measured and was found to be very sensitive to the magnetic properties at both the FM and AFM interfaces. Secondly, the recoil implantation of radioactive Fe probes into rare-earth hosts and d-band alloys and subsequent measurement using time-differential perturbed angular distribution offer the possibility of controlling the chemical composition and number of nearest-neighbours. This method was used to prepare local 3d-magnetic clusters in a non-magnetic matrix and to observe their magnetic behaviour. Finally, non-magnetic radioactive probes were 'soft-landed' onto Ni surfaces and extremely lattice-expanded ultrathin Ni films. By measuring the magnetic hyperfine fields and EFGs at 111 Cd probes using time-differential perturbed angular correlation (TDPAC), it was possible to distinguish the interaction of Cd probes located at various surface This article was invited by Professor S Washburn.

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Coordination-dependence of hyperfine interactions at impurities on fcc metal surfaces. II. Magnetic hyperfine field

et al. 2004

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We present a comparison between ab initio calculations and a high-quality experimental data set (1990-2002) of magnetic hyperfine fields of Cd at different sites on Ni surfaces. The experimentally observed parabolic coordination number dependence of this hyperfine field is verified as a general trend, but we demonstrate that individual cases can significantly deviate from it. It is shown that the hyperfine fields of other 5sp impurities at Ni surfaces have their own, typical coordination number dependence. A microscopic explanation for the different dependencies is given in terms of the details of the s-DOS near the Fermi level

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Surface and interface investigations using radioactive atoms

Cited by 4 publications

References 21 publications

Coordination dependence of hyperfine fields of 5sp impurities on Ni surfaces

Coordination dependence of hyperfine fields of 5sp impurities on Ni surfaces

Magnetic nanostructures: radioactive probes and recent developments

Coordination-dependence of hyperfine interactions at impurities on fcc metal surfaces. II. Magnetic hyperfine field

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