Influence of the stray field of a magnetic dot on the nucleation of superconductivity in a disk

Golubović, D.S.; Pogosov, W. V.; Morelle, Mathieu; Moshchalkov, Victor

doi:10.1209/epl/i2003-10121-4

Cited by 14 publications

(12 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed periodic cusp-like behavior of the T c (H ext ) dependence was attributed to the field-induced transition between states with different vorticity similar to that of mesoscopic superconductors in a uniform magnetic field. However, the stray field, induced by the magnetized dot, was shown to be responsible for a peculiar asymmetry of the oscillatory T c (H ext ) phase boundary and a shift of the main T c maximum towards nonzero H ext values [54,133,134,135]. The mentioned abrupt modification of the preferable nucleation regime when sweeping H ext can lead to a double change in the slope of the T c (H ext ) envelope from T c0 /H Fig.…”

Section: Little-parks Oscillations In Mesoscopic Samplesmentioning

confidence: 99%

Nucleation of superconductivity and vortex matter in superconductor–ferromagnet hybrids

Aladyshkin

Silhanek

Gillijns

et al. 2009

Supercond. Sci. Technol.

217

143

View full text Add to dashboard Cite

Abstract. The theoretical and experimental results concerning the thermodynamical and low-frequency transport properties of hybrid structures, consisting of spatially-separated conventional low-temperature superconductor (S) and ferromagnet (F), is reviewed. Since the superconducting and ferromagnetic parts are assumed to be electrically insulated, no proximity effect is present and thus the interaction between both subsystems is through their respective magnetic stray fields. Depending on the temperature range and the value of the external field Hext, different behavior of such S/F hybrids is anticipated. Rather close to the superconducting phase transition line, when the superconducting state is only weakly developed, the magnetization of the ferromagnet is solely determined by the magnetic history of the system and it is not influenced by the field generated by the supercurrents. In contrast to that, the nonuniform magnetic field pattern, induced by the ferromagnet, strongly affect the nucleation of superconductivity leading to an exotic dependence of the critical temperature Tc on Hext. Deeper in the superconducting state the effect of the screening currents cannot be neglected anymore. In this region of the phase diagram various aspects of the interaction between vortices and magnetic inhomogeneities are discussed. In the last section we briefly summarize the physics of S/F hybrids when the magnetization of the ferromagnet is no longer fixed but can change under the influence of the superconducting currents. As a consequence, the superconductor and ferromagnet become truly coupled and the equilibrium configuration of this "soft" S/F hybrids requires rearrangements of both, superconducting and ferromagnetic characteristics, as compared with "hard" S/F structures. Some figures in this paper are in color only in the electronic version.

show abstract

Section: Little-parks Oscillations In Mesoscopic Samplesmentioning

confidence: 99%

Nucleation of superconductivity and vortex matter in superconductor–ferromagnet hybrids

Aladyshkin

Silhanek

Gillijns

et al. 2009

Supercond. Sci. Technol.

217

143

View full text Add to dashboard Cite

show abstract

“…The transition from the GVS to a set of Φ 0 -vortices is caused by the reduced axial symmetry of squares and triangles and ensures that a vortex pattern conforms to the symmetry imposed by the boundary of the sample.In this paper we investigate the onset of superconductivity in a mesoscopic disk on which a magnetic triangle with out-of-plane magnetization is placed. The nucleation of superconductivity in hybrid superconductor/ferromagnet disks and loops has been studied previously, both experimentally and theoretically, as these are a good model system to gain insight into the interplay between superconductivity and magnetism in the context of magnetic vortex pinning and related phenomena [5,6,7,8]. In this paper we show that the symmetry of the magnetic triangle has a profound effect on the onset of superconductivity in the disk.…”

mentioning

confidence: 76%

Magnetically induced splitting of a giant vortex state in a mesoscopic superconducting disk

et al. 2005

View full text Add to dashboard Cite

The nucleation of superconductivity in a superconducting disk with a Co/Pt magnetic triangle was studied. We demonstrate that when the applied magnetic field is parallel to the magnetization of the triangle, the giant vortex state of vorticity three splits into three individual Φ0-vortices, due to a pronounced influence of the C3 symmetry of the magnetic triangle. As a result of a strong pinning of the three vortices by the triangle, their configuration remains stable in a broad range of applied magnetic fields. For sufficiently high fields, Φ0-vortices merge and the nucleation occurs through the giant vortex state. The theoretical analysis of this novel reentrant behaviour at the phase boundary, obtained within the Ginzburg -Landau formalism, is in excellent agreement with the experimental data. PACS numbers: 74.78.Na., 75.75.+a, 74.25.Dw The nucleation of superconductivity in mesoscopic samples, whose dimensions are comparable to the superconducting coherence length ξ(T ) and the penetration depth λ(T ), is substantially affected by the sample boundary (see Ref.[1] and references therein). It is well established that in circular mesoscopic disks and loops the onset of superconductivity mostly occurs through the giant vortex state (GVS) due to their cylindrical symmetry [2]. On the other hand, in superconducting squares and triangles for certain magnetic fields the GVS easily splits into individual Φ 0 -vortices (Φ 0 is the superconducting flux quantum), with a possible generation of additional antivortices [3]. The transition from the GVS to a set of Φ 0 -vortices is caused by the reduced axial symmetry of squares and triangles and ensures that a vortex pattern conforms to the symmetry imposed by the boundary of the sample.In this paper we investigate the onset of superconductivity in a mesoscopic disk on which a magnetic triangle with out-of-plane magnetization is placed. The nucleation of superconductivity in hybrid superconductor/ferromagnet disks and loops has been studied previously, both experimentally and theoretically, as these are a good model system to gain insight into the interplay between superconductivity and magnetism in the context of magnetic vortex pinning and related phenomena [5,6,7,8]. In this paper we show that the symmetry of the magnetic triangle has a profound effect on the onset of superconductivity in the disk. Due to the competition between the cylindrical symmetry of the superconducting disk and the C 3 symmetry of the stray field, superconductivity nucleates as a GVS for vorticity L = 2, whereas for L = 3 the GVS splits into three Φ 0 -vortices. As a result of a strong pinning of the three individual vortices their configuration remains stable for L = 4 and L = 5. FIG. 1: The calculated spatial profile (a) of the stray field and (b) a magnetic force micrograph of the triangle. The field values were calculated using the saturation magnetization of bulk Co.The sample was prepared by electron beam lithography, using double resist technique and lift-off in two steps. For details we ...

show abstract

“…As a result, superconductivity can be sustained in the sample up to very large FM-magnetization (as the slope ∂G/∂M decreases in 2). Note that this is not the case if FM has perpendicular magnetization, when total flux Φ F M captured by SC is positive and FM-induced vortices destroy superconductivity in the heart of the sample [8,9]. The experiment of Ref.…”

mentioning

confidence: 97%

“…The SC material is characterized by its coherence length at zero temperature, which we take as ξ(0) = 100nm (typical value for mesoscopic Al samples [8]), and FM material by its saturation magnetization M . In our calculations, the FM is positioned at the center of the SC square, and since its stray field has opposite polarity at the FM-poles (see inset (a) in Fig.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Mesoscopic Field and Current Compensator Based on a Hybrid Superconductor-Ferromagnet Structure

2005

View full text Add to dashboard Cite

A rather general enhancement of superconductivity is demonstrated in a hybrid structure consisting of submicron superconducting (SC) sample combined with an in-plane ferromagnet (FM). The superconducting state resists much higher applied magnetic fields for both perpendicular polarities, as applied field is screened by the FM. In addition, FM induces (in the perpendicular direction to its moment) two opposite current-flows in the SC plane, under and aside the magnet, respectively. Due to the compensation effects, superconductivity persists up to higher applied currents. With increasing current, the sample undergoes SC-"resistive"-normal state transitions through a mixture of vortex-antivortex and phase-slip phenomena.

show abstract

Influence of the stray field of a magnetic dot on the nucleation of superconductivity in a disk

Cited by 14 publications

References 13 publications

Nucleation of superconductivity and vortex matter in superconductor–ferromagnet hybrids

Nucleation of superconductivity and vortex matter in superconductor–ferromagnet hybrids

Magnetically induced splitting of a giant vortex state in a mesoscopic superconducting disk

Mesoscopic Field and Current Compensator Based on a Hybrid Superconductor-Ferromagnet Structure

Contact Info

Product

Resources

About