Anisotropic thermomagnetic avalanche activity in field-cooled superconducting films

Colauto, F.; Carmo, D.; Andrade, Ankilma do Nascimento; Oliveira, Alisson Macário de; Ortiz, W.A.; Johansen, T. H.

doi:10.1103/physrevb.96.060506

Cited by 8 publications

(11 citation statements)

References 26 publications

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“…In addition to the clear difference in the flux penetration depth from the two pairs of opposite edges, the image also reveals that the penetration has a clear filamentary character in the direction parallel to the frozen-in flux. This suggests that the motion of incoming perpendicular vortices is facilitated and guided by the in-plane vortices already present in the film, an observation fully consistent with MOI results reported recently [25]. In that work it was found that in terms of critical current densities the in-plane magnetic field has little influence on the magnitude of J L c .…”

Section: A Flux Penetration At 7 Ksupporting

confidence: 89%

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Active control of thermomagnetic avalanches in superconducting Nb films with tunable anisotropy

Carmo

Colauto

Andrade

et al. 2018

Supercond. Sci. Technol.

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Active triggering and manipulation of ultrafast flux dynamics in superconductors are demonstrated in films of Nb. Controlled amounts of magnetic flux were injected from a point along the edge of a square sample, which at 2.5 K responds by nucleation of a thermomagnetic avalanche. Magneto-optical imaging was used to show that when such films are cooled in the presence of in-plane magnetic fields they become anisotropic, and the morphology of the avalanches change systematically, both with the direction and magnitude of the field. The images reveal that the avalanching dendrites consistently bend towards the direction perpendicular to that of the in-plane field. The effect increases with the field magnitude, and at 1.5 kOe the triggered avalanche becomes quenched at the nucleation stage. The experimental results are explained based on a theoretical model for thermomagnetic avalanche nucleation in superconducting films, and by assuming that the frozenin flux generates in-plane anisotropy in the film thermal conductance. The results demonstrate that applying in-plane magnetic fields to film superconductors can be a versatile external tool for controlling their ultrafast flux dynamics.

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Section: A Flux Penetration At 7 Ksupporting

confidence: 89%

“…Interestingly, this image shows that the incipient stage of the runaway has a flux distribution quite different from that created by a current pulse at 7 K. The penetrated region has at 7 K the shape of a semicircle with radius close to the width of the legs of the injector. [25]. In Fig.…”

Section: Quenching Of Dendritesmentioning

confidence: 98%

Active control of thermomagnetic avalanches in superconducting Nb films with tunable anisotropy

Carmo

Colauto

Andrade

et al. 2018

Supercond. Sci. Technol.

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“…We have observed further that preplacement of magnetic flux with a two-step PFM technique may reduce the generation of heat, and hence moderate the extent of the region of instabilities. This reflects partly how the frozen-in vortices affect the magnetization of bulk samples [32].…”

Section: Introductionmentioning

confidence: 99%

Flux jumps in ring-shaped and assembled bulk superconductors during pulsed field magnetization

Zhou

Shi

Dennis

et al. 2020

Supercond. Sci. Technol.

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Bulk (RE)BCO, where RE is a rare-earth element or yttrium, superconductors fabricated in the form of rings are potentially useful for a variety of solenoidal-type applications, such as small, high field nuclear magnetic resonance and electromagnetic undulators. It is anticipated that the practical exploitation of these technologically important materials will involve pulse field magnetization (PFM) and, consequently, it is important to understand the behavior of ring-shaped samples subjected to the PFM process. Macroscopic flux jumps were observed in PFM experiments on ring-shaped bulk samples when the peak applied field reaches a threshold magnitude, similar to behavior reported previously in cylindrical samples. Magnetic flux jumps inward when the thermal instability is triggered, however it subsequently flows outwards from the sample, resulting in a relatively low trapped field. This behavior is attributed to a variety of effects, including the inhomogeneity of the material, which may lead to the formation of localized hot spots during the PFM process. In order to further elucidate this phenomena, the properties of a structure consisting of a bulk superconducting ring with a cylindrical superconductor core were studied. We observe that, although a flux jump occurs consistently in the ring, a critical state is established at the boundary of the ring-shaped sample and the core. We provide a detailed account of these experimental observations and provide an explanation in terms of the current understanding of the PFM process.

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“…A Fig.6.11 mostra a dependência genérica do campo magnético perpendicular limiar em função da corrente crítica para filmes supercondutores, onde pode-se observar que o fato de termos um incremento no campo limiar para o começo de avalanches de vórtices implica na diminuição da densidade de corrente crítica no supercondutor. Dessa forma, podemos afirmar que a presença de nanofios magnéticos na matriz porosa estaria contribuindo para a diminuição da corrente Figura 6.11: Curva genérica do campo perpendicular limiar para o inicio de avalanches termomagnéticas num filme supercondutor em função da densidade de corrente crítica [137,138]. crítica no filme supercondutor.…”

Section: Resultados Das Imagens Por Magneto-óticaunclassified

“…. 110 6.11 Curva genérica do campo perpendicular limiar para o inicio de avalanches termomagnéticas num filme supercondutor em função da densidade de corrente crítica [137,138]…”

Section: Introductionunclassified

Propriedades magnéticas e supercondutoras de redes de nanofios de Ni acopladas a filmes de Nb

Ayllon¹

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AgradecimentosEm primeiro lugar agradeço ao Prof. Daniel Cornejo pela oportunidade de trabalhar juntos, pelos ensinamentos ao longo deste caminho, pela paciência e constante suporte, e pela confiança e amizade durante todos estes anos.Agradezco a mis padres Rosario y Edgar, y a mis hermanos Juank y Miguel, por el apoyo constante y por comprender que grandes logros demandan grandes sacrificios. A mi abuelita Ória que cada día que pasa espera con ansias el volverme abrazar. A mi abuelito Carlos que estará presente siempre y que hoy me cuida desde allá arriba. A mi sobrinita Mia que me alegra los dias cada vez que veo sus fotos. A pipoquita que me espera con sus patitas listas para jugar. Gracias a toda mi familia por siempre creer en mi y acompañarme en esta jornada de locos.Ao pessoal do LMM, Sergio, Marcelo, Renato e Paulo, pelo suporte e ajuda no desenvolvimento experimental da minha pesquisa. Aos professores do grupo: Toninho, Luiz Nagamine e Carmen, por serem sempre prestativos.Ao Prof. Alain Quivy pela colaboração nas imagens de AFM. Ao Tarsis do laboratório de cristalografia do IFUSP pelas medidas de XRD. Ao pessoal do LAMFI pela colaboração nas medidas de RBS. Ao Prof. Fabiano Colauto pela colaboração e ensinamentos na técnica de imagens magneto-óticas. Ao pessoal da cpg pela ajuda e orientações ao longo desses anos.Aos meus amigos peruanos "The Hobbits": Lindber, Jose, Angel, Rene, Hector, Carloncho, Heyner, Victor, Naupa e Juancito por todos os momentos divertidos. Aos meus colegas e amigos do IFUSP: pelo companheirismo e amizade durante todos estes anos.A Isabel pelo carinho, apoio, paciência e força durante a etapa final deste trabalho. E por ser a minha companheira, aquela que me faz sorrir. E por fim, agradecer a CNPq pelo apoio financeiro, sem o qual não teria condições de realizar este trabalho.T c do supercondutor, mas quando a temperatura é diminuída a penetração de fluxo adota um perfil dendrítico aleatório.Palavras-chave: Física da matéria condensada; magnetismo; supercondutividade; filmes finos; aprisionamento de vórtices. AbstractIn this work we have studied the magnetic properties of a system formed by a Nb thin film deposited on top of an array of ferromagnetic Ni nanowires embedded in a ordered porous alumina membrane as substrate. The substrates were obtained by the two-step anodization technique, followed by an electrodeposition AC of the ferromagnetic material. The Nb film was deposited via magnetron sputtering. The magnetic response of this system was investigated over a wide range of temperatures through AC susceptibility, DC magnetization and magneto-optical images (MOI) measurements.Initially, the magnetic properties of Ni nanowire system were studied. We perform magnetization measurements above the superconducting transition temperature of Nb, in the range of 10 to 300 K where the superconducting film does not contribute to magnetization. These results showed the strong uniaxial character of the effective anisotropy in such systems, as well as its dependence on the temperature and t...

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Anisotropic thermomagnetic avalanche activity in field-cooled superconducting films

Cited by 8 publications

References 26 publications

Active control of thermomagnetic avalanches in superconducting Nb films with tunable anisotropy

Active control of thermomagnetic avalanches in superconducting Nb films with tunable anisotropy

Flux jumps in ring-shaped and assembled bulk superconductors during pulsed field magnetization

Propriedades magnéticas e supercondutoras de redes de nanofios de Ni acopladas a filmes de Nb

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