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Röhlsberger, Ralf

doi:10.1023/a:1017063605078

Cited by 51 publications

(33 citation statements)

References 23 publications

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“…In the resonant refl ectivity curve, however, four magnetic Bragg peaks can be identifi ed. The red curves in Figure 3 B are simulations of both refl ectivity curves using a layer matrix formalism [28][29][30] and fi nally prove that the desired spin profi le is realized with a precision better than 2° throughout the whole layer stack as determined by the parameters of the deposition process.…”

Section: Magnetic Anisotropy Control In Single Films Via Oblique Incimentioning

confidence: 70%

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Schlage

Bocklage

Erb

et al. 2016

Adv Funct Materials

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7423wileyonlinelibrary.com extensively explored to maximize the magnitude of the magnetoresistive signal, which is defi ned as the normalized difference of the electrical resistance in the antiparallel and parallel magnetic confi guration of the trilayer. The basic GMR and TMR characteristics of spintronic devices and thus their functionalities, however, did not signifi cantly change during the last decade. This is due to conventional magnetic multilayer design and its limitations based on the interplay of accessible magnetic anisotropy contributions. Here, we show that oblique incidence deposition (OID) can be used in an elegant way to achieve full control on the magnetic anisotropy in every individual layer of such magnetoresistive multilayer stacks for the fi rst time. The additional shape anisotropy component introduced via OID allows for arbitrarily crossed magnetic easy axes with adjustable switching fi elds and opens a path for customized spintronic devices with conceptually new functionalities.So far, two major approaches have been pursued to engineer fi eld-dependent relative magnetic confi gurations of two ferromagnetic layers. In the fi rst case, one of the ferromagnetic layers either exhibits an enhanced coercive fi eld or is magnetically pinned (exchange biased) by an additional antiferromagnetic layer of high magnetic anisotropy. Thus, only the magnetically uncoupled free layer follows small external fi elds, causing a change of the magnetic confi guration and the magnetoresistance. [ 13 ] In the second approach, an interlayer exchange coupling, the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction, is used to align both layers relative to each other. [ 14 ] The interlayer coupling defi nes the magnetic saturation behavior and hence the functionality of the trilayer. In conventional systems, only parallel or antiparallel orientations of the ferromagnetic layers are reliably achieved. Effi cient RKKY coupling is observed for particular material combinations only and depends very sensitively on the interlayer thickness. [ 15,16 ] Therefore, conventional magnetic multilayer design is restricted to a limited number of magnetic confi gurations in the trilayers which constrains the design and control of magnetic spin structures that are available for realizing particular magnetoelectronic responses.Our approach enables one to realize and tune magnetic and magnetoresistive properties in spintronic multilayer systems that exceed the potential of conventional approaches by far. The technique is not based on exchange-bias or interlayer coupling and is not affected by their limitations. Every ferromagnetic layer of arbitrary chemical composition, as a constituent either Spin-Structured Multilayers: A New Class of Materials for Precision SpintronicsKai Schlage , * Lars Bocklage , Denise Erb , Jade Comfort , Hans-Christian Wille , and Ralf Röhlsberger * Magnetoelectronic multilayer devices are widely used in today's information and sensor technology. Their functionality, however, is limited by the inherent prop...

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Section: Magnetic Anisotropy Control In Single Films Via Oblique Incimentioning

confidence: 70%

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Schlage

Bocklage

Erb

et al. 2016

Adv Funct Materials

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“…All quantum model results using the formalism in Ref. [37] have been double-checked and confirmed by comparison with simulations with the software package CONUSS [43] implementing a self-consistent theory including multiple scattering to all orders [44].…”

mentioning

confidence: 99%

Collective radiation spectrum for ensembles with Zeeman splitting in single-photon superradiance

Kong

Pálffy

2017

Phys. Rev. A

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In an ensemble of identical atoms, cooperative effects like sub-or superradiance may alter the decay rates and the energy of specific transitions may be shifted from the single-atom value by the so-called collective Lamb shift. While such effects in ensembles of two-level systems are by now well understood, realistic multi-level systems are more difficult to handle. In this work we show that in a system of atoms or nuclei under the action of an external magnetic field, the collective contribution to the level shifts can amount to seizable deviations from the single-atom Zeeman or magnetic hyperfine splitting picture. We develop a formalism to describe single-photon superradiance in multi-level systems in the small sample limit and quantify the parameter regime for which the collective Lamb shift leads to measurable deviations in the magnetic-field-induced splitting. In particular, we show that this effect should be observable in the nuclear magnetic hyperfine splitting in Mössbauer nuclei embedded in thin-film x-ray cavities. PACS numbers: 78.70.Ck, 42.50.Nn, 76.80.+y 32.30.Dx In 1947, a famous experiment by Lamb and Retherford [1] confirmed that the 2s 1/2 and 2p 1/2 levels in hydrogen are not degenerate, leading to increased efforts in the theoretical understanding of radiation quantization [2,3] and to the development of quantum electrodynamics (QED) [4]. Today, it is known that this small shift has to do with emission and reabsorption of virtual photons within the atom, mainly with selfenergy and vacuum-polarization corrections. Interestingly, it could be shown that an additional contribution arises if many identical atoms are interacting collectively with resonant photons, and virtual photons are exchanged between different atoms [5][6][7][8][9][10]. This additional contribution has been termed in analogy collective Lamb shift, although the exact underlying processes share with the single-atom Lamb shift mechanism only the virtual character of the photons being exchanged.The collective Lamb shift has been investigated theoretically for ensembles of two-level systems in the small and large sample limits [5,[11][12][13][14][15]. Collective scattering of a weakintensity laser off a cold ensemble of rubidium atoms with Zeeman splitting has been recently investigated both theoretically and experimentally [16][17][18][19], with results that partly contradict predictions of the standard cooperative Lamb shift theory. In the context of ensembles of atoms in magnetic fields, a legitimate question is to which extend can the Zeeman splitting be considered independently from the cooperative effects and in particular the collective Lamb shift. In this Letter, we show that in ensembles of atoms or nuclei with magneticfield induced level multiplets, the collective magnetic splitting can show significant deviations of the Zeeman splitting compared to the single-atom behaviour and cannot be justified by mere two-level system collective Lamb shift contributions for each transition independently, as done for instance in Re...

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“…(The detailed description is given in [25]). The procedure of the roughness inclusion to the matrix reflectivity theory, described in [38], is much more complicated and uncertain for differential consideration of the separate hyperfine contributions.…”

Section: ˆ( ) 4sinmentioning

confidence: 99%

Field-induced spin reorientation in[Fe/Cr]nmultilayers studied by nuclear resonance reflectivity

et al. 2015

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We present the depth-resolved nuclear resonance reflectivity (NRR) studies of the magnetization evolution in [ 57 Fe(3 nm)/Cr(1.2 nm)] 10 multilayer under the applied external field. The measurements have been performed at the station BL09XU of SPring-8 at different values of the external field (0 -1500 Oe). We apply the joint fit of the delayed reflectivity curves and the time spectra of the nuclear resonance reflectivity measured at different grazing angles for enhancement of the depth resolution and reliability of the results. For the first time we show that the azimuth angle, which is used in all papers devoted to the magnetization profile determination, has more complicated physical sense due to the partially coherent averaging of the scattering amplitudes from magnetic lateral domains. We describe the way how to select the true azimuth angle from the determined "effective azimuth angle". Finally we obtain the noncollinear twisted magnetization depth-profiles where the spin flop state appears sequentially in different 57 Fe layers at increasing applied field.

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Untitled

Cited by 51 publications

References 23 publications

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Collective radiation spectrum for ensembles with Zeeman splitting in single-photon superradiance

Field-induced spin reorientation in[Fe/Cr]nmultilayers studied by nuclear resonance reflectivity

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