Nanostructures: Scattering beyond the Born approximation

Grigoriev, S. V.; Syromyatnikov, A. V.; Chumakov, Andrei; Grigoryeva, N. A.; Napolskii, K. S.; Roslyakov, Ilya V.; Eliseev, A. A.; Petukhov, Andrei V.; Eckerlebe, H.

doi:10.1103/physrevb.81.125405

Cited by 29 publications

(25 citation statements)

References 22 publications

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“…In the IMS, the intensity depends further on the reduced area of SS regions, while the peaks broaden due to the finite size of VL domains. Note, that the observed correlation length is much larger for small angle diffraction [42], compared to diffuse SANS [43].…”

Section: Acknowledgmentsmentioning

confidence: 91%

“…The VL-correlation length ξ V L obtained from SANS measurements was determined from the width of the first order Bragg-peaks ∆q Bragg in q-direction. It was corrected by the reciprocal space resolution ∆q Inst according to [34,42] as ∆q = ∆q 2 Bragg − ∆q 2 Inst . The VLcorrelation length is then defined as ξ V L = (2π)/(∆q) The Bragg peak positions are defined by the VL arrangement (structure factor).…”

Section: Acknowledgmentsmentioning

confidence: 99%

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Universal behavior of the intermediate mixed state domain formation in superconducting niobium

et al. 2019

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In the intermediate mixed state (IMS) of type-II/1 superconductors, vortex lattice (VL) and Meissner state domains coexist due to a partially attractive vortex interaction. Using a neutronbased multiscale approach combined with magnetization measurements, we study the continuous decomposition of a homogeneous VL into increasingly dense domains in the IMS in bulk niobium samples of varying purity. We find a universal temperature dependence of the vortex spacing, closely related to the London penetration depth and independent of the external magnetic field. The rearrangement of vortices occurs even in the presence of a flux freezing transition, i.e. pronounced pinning, indicating a breakdown of pinning at the onset of the vortex attraction.Conventional superconductors are divided by the Ginzburg-Landau parameter κ into type-I (κ < 1/ √ 2) and type-II (κ > 1/ √ 2), which, additionally to the Meissner state (MS) exhibit the Shubnikov state (SS). In the SS, magnetic vortices form a variety of vortex matter (VM), such as the Abrikosov vortex lattice (VL) [1], glassy [2][3][4] or liquid [5][6][7] states. Type-II superconductors are further subdivided, where type-II/2 (κ 1/ √ 2) features a purely repulsive inter-vortex interaction. In type-II/1(κ ≈ 1/ √ 2) the interaction acquires an attractive component [8][9][10], which favors the formation of vortex clusters, leaving behind MS regions. The resulting domain structure is denoted the intermediate mixed state (IMS).The IMS in the type-II/1 superconductor niobium (Nb) is an ongoing research topic since its first observation via Bitter decoration in 1967 [11,12]. Despite numerous experimental [9, 13-16] and theoretical [8, 10, 17, 18] efforts, its properties are not yet fully understood. The interplay of repulsive and attractive vortex interactions and the consequences on the domain structure in superconducting VM have found renewed interest with the discovery of multiband superconductors, especially MgB 2 (sometimes denoted as type-1.5) [19]. Apart from superconducting properties, the IMS is also a model system for universal domain physics [20], as it can be tuned readily by temperature and magnetic field [21].Previous studies primarily investigated the zero field cooled (ZFC) field dependence of the IMS. However, this approach leads to strong magnetic inhomogeneities due to geometric and demagnetization effects reflected in the critical state model [22,23]. In contrast, our systematic study focuses on the temperature dependence during a field cooling (FC) and subsequent field heating (FC/FH) protocol in bulk Nb samples with distinct pinning properties. The phase diagram and the transition from a ho- * alexander.Backs@frm2.tum.de † sebastian.muehlbauer@frm2.tum.de mogeneous VL in the SS to the increasingly dense VL domains in the IMS is sketched in Fig. 1 on a FC path. FIG. 1.Schematic phase diagram of a type-II/1 superconductor, subdivided into MS, IMS and SS. Arrows depict different measurement protocols: FC, FC/FH and ZFC/FH. For FC measurements, the microscopic magnet...

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Section: Acknowledgmentsmentioning

confidence: 91%

Section: Acknowledgmentsmentioning

confidence: 99%

Universal behavior of the intermediate mixed state domain formation in superconducting niobium

et al. 2019

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“…In some cases, especially in low-symmetry crystals, t z = t z (k x , k y ) depends on in-plane momentum, which affects AMRO and MQO. [22][23][24][25] However, to describe most compounds it is sufficient to take t z (k x , k y ) ≈ const. The geometrical explanation of AMRO 5 for the electron dispersion in Eq.…”

Section: Introductionmentioning

confidence: 99%

False spin zeros in the angular dependence of magnetic quantum oscillations in quasi-two-dimensional metals

Grigoriev

Mogilyuk

2017

Phys. Rev. B

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The interplay between angular and quantum magnetoresistance oscillations in quasi-twodimensional metals leads to the angular oscillations of the amplitude of quantum oscillations. This effect becomes pronounced in high magnetic field, when the simple factorization of the angular and quantum oscillations is not valid. The amplitude of quantum magnetoresistance oscillations is reduced at the Yamaji angles, i.e. at the maxima of the angular magnetoresistance oscillations. These angular beats of the amplitude of quantum oscillations resemble and may be confused with the spin-zero effect, coming from the Zeeman splitting. The proposed effect of "false spin zeros" becomes stronger in the presence of incoherent channels of interlayer electron transport and can be used to separate the different contributions to the Dingle temperature and to check for violations from the standard factorization of angular and quantum magnetoresistance oscillations. PACS numbers: 72.15.Gd,73.43.Qt,74.70.Kn, ρ F = m * /π 2 d is the 3D density of states (DoS) at the Fermi level in the absence of magnetic field per two spin components, and the mean squared interlayer electron velocity along interlayer direction is v 2 z = 2t 2 z d 2 / 2 .

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“…Previously, small angle neutron scattering from an AAO matrix was theoretically described in [32]. It was shown that description of the scattering process is beyond the scope of the Born approximation.…”

Section: Introductionmentioning

confidence: 99%

Polarized-neutron scattering from an array of magnetic nanowires embedded into a nonmagnetic matrix

Iashina

Grigoryeva

Dubitskiy

et al. 2015

J. Synch. Investig.

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Neutron scattering from spatially ordered arrays of magnetic nanowires synthesized inside a non magnetic matrix is theoretically described. Expressions for the nuclear, magnetic, and interference contribu tions to the neutron scattering cross section are obtained. It is shown that, when polarized neutrons are scat tered from an array of magnetic nanowires, the scattering cross section is not only a nonlinear function of the nanowire length but also depends on the neutron wavelength. These expressions describe the complex nature of the neutron diffraction pattern as a factor of the ratio of nuclear and magnetic scattering amplitudes.Keywords: small angle polarized neutron scattering, magnetic properties of anisotropic nanoparticles, spa tially ordered arrays of magnetic nanowires

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Nanostructures: Scattering beyond the Born approximation

Cited by 29 publications

References 22 publications

Universal behavior of the intermediate mixed state domain formation in superconducting niobium

Universal behavior of the intermediate mixed state domain formation in superconducting niobium

False spin zeros in the angular dependence of magnetic quantum oscillations in quasi-two-dimensional metals

Polarized-neutron scattering from an array of magnetic nanowires embedded into a nonmagnetic matrix

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