Flux pinning enhancement in ferromagnetic and superconducting thin-film multilayers

Jan, D. B.; Coulter, J. Y.; Hawley, M. E.; Bulaevskiǐ, L. N.; Maley, M. P.; Jia, Q. X.; Maranville, Brian B.; Hellman, F.; Pan, Xiaoqing

doi:10.1063/1.1542674

Cited by 70 publications

(47 citation statements)

References 15 publications

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“…(693) Several experimental studies confirmed that this type of pinning enhancement occurs, both in multilayers and in the FM/SC bilayers (FSBs) [2][3][4][5][6]. In particular, we have studied the FSBs consisting of Nb film deposited on the top of Co/Pt multilayer, and we found that the pinning is enhanced exclusively in the final stages of the magnetic reversal process of the FM layer.…”

Section: Introductionmentioning

confidence: 79%

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

et al. 2004

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The local flux profile and the critical current are studied using an array of Hall sensors in a ferromagnetic-superconducting bilayer which consists of niobium film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. The results indicate about threefold enhancement of the flux pinning in niobium layer caused by the isolated magnetic domains which are created during the magnetization reversal of the Co/Pt multilayer. The geometrical barrier is absent, and the critical current is strongly peaked in close vicinity to the sample center, suggesting that the critical state differs from that predicted by the Bean model.

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Section: Introductionmentioning

confidence: 79%

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

et al. 2004

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“…The interaction between vortices and pinning centers has been studied extensively for decades, focused mainly on the so-called vortex core pinning (caused by the local suppression of the superconducting order parameter) [1,2]. Less explored is the interplay between vortices and magnetic media, which could offer pinning forces superior to those from core pinning [3][4][5][6]. A common difficulty of studying magnetic pinning is the inability of separating the magnetic and core contributions.…”

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confidence: 99%

Strong enhancement of the critical current at the antiferromagnetic transition in ErNi2B2C single crystals

Weigand

Civale²,

Baca³

et al. 2013

Phys. Rev. B

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We report on transport and magnetization measurements of the critical current density Jc in ErNi2B2C single crystals that show strongly enhanced vortex pinning at the Néel temperature TN and low applied fields. The height of the observed Jc peak decreases with increasing magnetic field in clear contrast with that of the peak effect found at the upper critical field. We also performed the first angular transport measurements of Jc ever conducted on this compound. They reveal the correlated nature of this pinning enhancement, which we attribute to the formation of antiphase boundaries at TN . 74.25.Sv, 74.25.Wx, 74.70.Dd Single quanta of magnetic flux enter a type II superconductor in the form of vortices when it is exposed to a magnetic field H. This is a big setback for applications, because when an electrical current J is applied, vortices move and energy is dissipated. This movement can be arrested by non-superconducting defects that pin vortices by lowering the system energy. The interaction between vortices and pinning centers has been studied extensively for decades, focused mainly on the so-called vortex core pinning (caused by the local suppression of the superconducting order parameter) [1,2]. Less explored is the interplay between vortices and magnetic media, which could offer pinning forces superior to those from core pinning [3][4][5][6]. A common difficulty of studying magnetic pinning is the inability of separating the magnetic and core contributions. It is, therefore, of great advantage to study systems where the magnetic transition takes place inside the superconducting phase, allowing one to compare the behavior with and without the magnetically ordered phase.There are a considerable number of materials in which to study the coexistence between superconductivity and ordered magnetic phases, such as the Chevrel-phases [7], CeCoIn 5 [8], and recently iron pnictides [9][10][11]. However, the rare earth-nickel-borocarbide family (RENi 2 B 2 C, where RE is a rare earth element) [12][13][14] has several advantages, namely a relatively high superconducting transition temperature T c and the tunability of the ratio between its magnetic and superconducting ordering temperatures, which can be changed by using different rare earth elements [15,16]. The readily available high-purity single crystals allow one to study the effects of magnetic pinning without any significant defect (non-magnetic) contribution [15].Among the borocarbide family the compound with RE = Er has a T c of 10.5 K and a Néel temperature T N of 6.0 K [17]. The occurrence of antiferromagnetism directly influences the superconducting properties, as seen in the upper critical field vs temperature curve, where H c2 (T ) is slightly suppressed just below T = T N for H c and has an inflection point for H ab [17]. This is a consequence of the local moments ordering in the antiferromagnetic phase, as was shown experimentally [17,18] and theoretically [19,20].In addition to the occurrence of antiferromagnetism, at T = T N a tetragonal to ortho...

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“…The two macroscopic quantum states in S and F layers influence each other via the penetration of superconducting (proximity effect) 2 and ferromagnetic (inverse proximity effect) [3][4][5] order through their common interface. In presence of strong enough magnetic fields, the vortices in the S-layer can couple with the magnetic domains of the F-layer leading to interesting effects of domain wall pinning of the vortices and vice-a-versa, and domain wall superconductivity [6][7][8][9][10] . Most of such studies have been carried out with ferromagnetic component consisting of 3d transition metals like Fe, Co and Ni, and their alloys.…”

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confidence: 99%

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

et al. 2013

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Proximity coupling and magnetic switching dynamics are shown to be correlated in bilayers (B) of fully spin polarized ferromagnet (F) Co 2 FeSi and superconductor (S) NbN. The upper critical field derived from resistivity measurements shows a dimensional crossover with a reduced effective thickness of the S layer. At temperatures (T) << superconducting T c , the measured M-H loops show two step switching; one at T-independent value 7 Oe and other at strongly T-dependent value becoming very large 1 kOe at 2 K. These results reveal induced ferromagnetism in S-layer at the S/F interface with vortex pinning influenced dynamics.PACS numbers: 74.45.+c, 74.78.-w, 74.25.Op 2The research field of superconducting (S) and ferromagnetic (F) bilayers (FSB), trilayers and multilayers has gained tremendous importance 1 due to their potential for magnetoeletronics related applications 2 ranging from spin valve to Josephson junctions based devices. The two macroscopic quantum states in S and F layers influence each other via the penetration of superconducting (proximity effect) 2 and ferromagnetic (inverse proximity effect) 3-5 order through their common interface. In presence of strong enough magnetic fields, the vortices in the S-layer can couple with the magnetic domains of the F-layer leading to interesting effects of domain wall pinning of the vortices and vice-a-versa, and domain wall superconductivity [6][7][8][9][10] . Most of such studies have been carried out with ferromagnetic component consisting of 3d transition metals like Fe, Co and Ni, and their alloys. Bilayers of strongly type II superconductors with fully spin polarized ferromagnetic (FSPF) Heusler alloys, which ideally have only one spin state and can potentially show fascinating electronic properties, have not been studied yet. Recently, our group has explored the use of the Co-based Heusler compound (Co 2 MnSi) electrodes for efficient injection of pure spin currents into superconducting NbN 11 . NbN is a type II superconductor of short coherence length ( (0) 5 nm) and long penetration depth ( (0) 200 nm) while Co 2 FeSi (CFS) is a ferromagnet of the Heusler family with high magnetic ordering temperature 1150 K and saturation magnetization 6 µ B per formula unit 12 . In the present work we investigate the nature of proximity coupling and its influence on magnetic switching dynamics in the hitherto unexplored NbN/Co 2 FeSi bilayers grown on (100) MgO.Thin film bilayers of superconducting NbN and CFS were deposited by pulsed laser ablation (PLD). The 35 nm thick NbN film first deposited on MgO at 200 0 C in nitrogen environment by ablating 99.99 % Nb target and then CFS layer of 35 nm thick was grown at the same temperature from a stoichiometric CFS target. To establish the magnetic ordering in CFS film, the FSB sample was annealed at 500 0 C for 1 hour. For comparison, a pure NbN film was also grown during the same PLD run. The other growth parameters for NbN and Co 2 FeSi layers can be found in our previous reports 13,14 . The crystalline quality and interf...

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Flux pinning enhancement in ferromagnetic and superconducting thin-film multilayers

Cited by 70 publications

References 15 publications

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

Strong enhancement of the critical current at the antiferromagnetic transition in ErNi2B2C single crystals

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

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Flux pinning enhancement in ferromagnetic and superconducting thin-film multilayers

Cited by 70 publications

References 15 publications

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

Strong enhancement of the critical current at the antiferromagnetic transition in ErNi2B2C single crystals

Giant coercivity enhancement and dimensional crossover of superconductivity in Co2FeSi-NbN nanoscale bilayers

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Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers