Composition gradient as a source of pinning in Nb–Ti and NbTa–Ti superconductors

Bormio-Nunes, Cristina; Sandim, Maria José Ramos; Ghivelder, L.

doi:10.1088/0953-8984/19/44/446204

Cited by 11 publications

(8 citation statements)

References 17 publications

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“…In the other scenario proposed by Bormio-Nunes et al [14], there are actually two kinds of strong pinning centers: one is the -Ti normal interface, and the other one is identified in the Nb and Ti composition gradients around the -Ti precipitates. Within this picture, the high-field pinning component of Fig.…”

Section: Discussionmentioning

confidence: 92%

“…Two possible scenarios for the pinning mechanisms in NbTi have been proposed in literature [11], [14]. Meingast et al [11] consider the idea that in optimized NbTi strands the pinning centers are clusters of -Ti ribbons, which give rise to fluctuations in both Ginzburg-Landau parameter and the thermodynamic critical field .…”

Section: Discussionmentioning

confidence: 99%

“…In particular, it is essential to extend the measurements over a wider temperature range, in order to verify that the observed small systematic shift of the peak toward lower reduced fields is definitely to be ascribed to a lack of scaling. In addition, dedicated heat treatments (HTs) [14] will be applied, in order to support the identification of the pinning mechanisms. Even if the microstructure variations due to HT seem to have no effects on at high temperatures and high fields [18], the HT could modify the relative weight ( in (3)) of the two components in the overall pinning force.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Pinning Properties of Commercial Nb-Ti Wires Described by a 2-Components Model

Muzzi

Marzi

Zignani

et al. 2010

IEEE Trans. Appl. Supercond.

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Abstract-We report on the magnetic and transport characterization of different NbTi commercial strands, carried out at variable temperature and magnetic field. From the critical current densities extracted from transport measurements and magnetization cycles we were able to calculate the normalized bulk pinning forces. The curves show good temperature scaling throughout the explored temperature range, and the reduced pinning force can be described by a simple two-components model system. The extension of the 2-components description of the pinning force to an expression for the critical current density gives a very good agreement with experimental measurements over the whole explored B, T range. The model works for all investigated samples, which are different in size, Cu:nonCu ratios, filament diameters and layouts. These results suggest that pinning mechanisms in conventional NbTi strands should be revised, since Nb-Ti composition gradients and grain boundaries seems to play a not negligible role.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Pinning Properties of Commercial Nb-Ti Wires Described by a 2-Components Model

Muzzi

Marzi

Zignani

et al. 2010

IEEE Trans. Appl. Supercond.

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“…Gradient composition materials, such as films or bulk, play important roles in the fields of many functional materials like shape memory alloys or semiconductors 10 11 12 . Because of the wide gradation of physical and chemical properties, the crystal structure and orientation are regulated, which then affects the magnetic properties of nanowires 13 .…”

mentioning

confidence: 99%

Static and Dynamic Magnetization of Gradient FeNi Alloy Nanowire

Yang

Zeng

et al. 2016

Sci Rep

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FeNi binary nanowires with gradient composition are fabricated by the electrodeposition method. The energy dispersive spec-trometer line-sweep results show that the composition changes gradually along the wire axis. The gradient FeNi nanowires exhibit polycrystalline and crystal twinning at different areas along the nanowire axis, with a textured face-centered cubic structure. The static and dynamic magnetization properties are characterized by a hysteresis loop and ferromagnetic reso-nance with pumping frequencies from 12– 40 GHz. The linear dispersion of the pumping frequency vs: the resonance field has been observed with the applied bias field higher than the saturation field, corresponding to the hysteresis loop. The field-sweep linewidths decrease with increasing pumping frequency, and the frequency-sweep linewidths stay nearly constant at the unsaturated region. The linewidth is a Gilbert type at the saturated state, with damping of 0.035 ± 0.003. Compared with the damping of the homogeneous composition FeNi nanowire (a = 0.044 ± 0.005), the gradient FeNi nanowire may have less eddy current damping, which could make it an alternative candidate for spintronics and microstrip antennas.

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“…As discussed in [11], we believe that the two possible types of strong pinning defects might be identified with clusters of ribbons [21], dominating at low reduced fields, and to Nb/Ti concentration gradients present around them [22], responsible for the behavior at high reduced fields.…”

Section: Data Analysis By Means Of the 2-pinning Components Modelmentioning

confidence: 79%

Test Results of a NbTi Wire for the ITER Poloidal Field Magnets: A Validation of the 2-Pinning Components Model

Muzzi

Marzi

Zignani

et al. 2011

IEEE Trans. Appl. Supercond.

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A two-components model has been recently developed, for describing the normalized bulk pinning force curves and the critical current density of NbTi strands over a wider B-T range with respect to conventional single-component models. The model was previously successfully applied to data collected on several NbTi commercial strands, with different size, Cu:nonCu ratio, filament diameter and layout, thus confirming the presence of two different pinning mechanisms in conventionally processed NbTi wires. For a further validation, we have extensively tested a strand recently produced by the Chinese Company Western Superconducting Technologies for the ITER Poloidal Field (PF) magnets PF2 to PF5, and applied the model to these data. In order to take into account the observed non-scaling with temperature of the reduced pinning force curves, the model has been updated, including the observed difference in the temperature dependences of the two components contributing to the overall bulk pinning force. The importance of testing wires over very wide temperature ranges is evidenced, and the good agreement between experimental and fit results validate the proposed formulation, which can be regarded as a reliable tool for the description of NbTi performances, to be used in the design of superconducting magnets. From the phenomenological point of view, it is shown that at low temperatures, the two pinning mechanisms contribute to the bulk pinning force, resulting in a pinning force peaking at a reduced field . As the temperature increases, the pinning force peak moves to lower fields, indicating that the low field component pinning mechanism becomes dominant.

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Composition gradient as a source of pinning in Nb–Ti and NbTa–Ti superconductors

Cited by 11 publications

References 17 publications

Pinning Properties of Commercial Nb-Ti Wires Described by a 2-Components Model

Pinning Properties of Commercial Nb-Ti Wires Described by a 2-Components Model

Static and Dynamic Magnetization of Gradient FeNi Alloy Nanowire

Test Results of a NbTi Wire for the ITER Poloidal Field Magnets: A Validation of the 2-Pinning Components Model

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