Magnetization Controlled Superconductivity in a Film with Magnetic Dots

Lyuksyutov, I. F.; Pokrovsky, V. L.

doi:10.1103/physrevlett.81.2344

Cited by 95 publications

(124 citation statements)

References 19 publications

(32 reference statements)

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“…and V.L.P.) proposed to separate superconductivity and magnetism in space employing the modern technique of nanofabrication [2]. The proximity effect which suppresses both order parameters can be easily avoided by growing insulator oxide layers between ferromagnetic (FM) and superconducting (SC) components.…”

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confidence: 99%

“…The magnetic field from the SC currents interacts with magnetic subsystem [3,4]. We have proposed different realizations of mesoscopic magneto-superconducting systems: arrays of magnetic dots on the top of a superconducting film [2], magnetic/superconducting bi-layers [3], magnetic nanorods embedded into a superconductor [4].…”

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confidence: 99%

“…The fabrication and experimental study [1] of mesoscopic heterogeneous magnetic/superconducting systems together with recent theoretical predictions [2][3][4] open a new class of physical effects. Earlier two of us (I.F.L.…”

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Interaction of mesoscopic magnetic textures with superconductors

et al. 2002

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We analyze magnetic textures in a thin magnetic film and screening currents induced by these textures in a superconducting film. The two films are supposed to be parallel and close each to other, but interact only via magnetic fields. We consider also vortices inside superconducting film and their interaction with magnetic textures. As examples of magnetic textures we consider magnetic dot and magnetic vortex. We derive the condition at which spontaneous formation of a vortex or a coupled vortex-magnetic defect is energetically favorable. It is proven that the normal component of magnetic field generated by a magnetic dot changes sign in the presence of the superconducting vortex.74.60. Ge, 74.25.Ha, 74.25.Dw The fabrication and experimental study [1] of mesoscopic heterogeneous magnetic/superconducting systems together with recent theoretical predictions [2][3][4] open a new class of physical effects. Earlier two of us (I.F.L. and V.L.P.) proposed to separate superconductivity and magnetism in space employing the modern technique of nanofabrication [2]. The proximity effect which suppresses both order parameters can be easily avoided by growing insulator oxide layers between ferromagnetic (FM) and superconducting (SC) components. Inhomogeneous magnetization of the magnetic texture generates magnetic field penetrating into the superconductor. The magnetic field from the SC currents interacts with magnetic subsystem [3,4]. We have proposed different realizations of mesoscopic magneto-superconducting systems: arrays of magnetic dots on the top of a superconducting film [2], magnetic/superconducting bi-layers [3], magnetic nanorods embedded into a superconductor [4].In the majority of proposed systems a magnetic texture interacts with the superconducting current. An inhomogeneous magnetization generates magnetic field outside the magnet. The magnetic field generates screening currents in superconductors which, in turn, change the magnetic field. The problem must be solved self-consistently . In this article we develop a general formalism for interacting inhomogeneous magnetization (texture) and superconductors in the London's approximation. Employing this formalism, we find two elementary solutions for a circular magnetic dot on the top of a superconducting film, magnetized perpendicularly to it, and for a coupled magnetic and superconducting vortices. London's approximation works satisfactory since the sizes of all structures in the problem exceeds remarkably the coherence length ξ.Recent theoretical works [5][6][7] consider problems close to ours. The main difference between our work and the Ref.[6] is that they do not incorporate spontaneous vortices in the ground state. In comparison to the Refs. [5,7] our approach is more general and universal. A more detailed comparison with these references will be given later.So far only arrays of sub-micron size magnetic dots covered by thin superconducting films have been prepared and studied experimentally [1] * * . The effect of commencuracy on the transport properti...

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Interaction of mesoscopic magnetic textures with superconductors

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“…The aforementioned systems are not only important for technological applications, such as devices that can be tuned by weak magnetic fields, but also offer rich physical effects which are not observed in the individual parts. Some of these effects were predicted elsewhere [2][3][4][5][6][7].In the recent decade, magnetic dots growing on top of SC films have been extensively studied both experimentally [8] and theoretically [9,10]. In experimental studies, magnetic dots with in-plane magnetization are fabricated from Co, Ni, Fe, Gd-Co and Sm-Co alloys, whereas, for the dots with magnetization perpendicular to the plane, Co/Pt multilayers are used [11].…”

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London study of vortex states in a superconducting film due to a magnetic dot

Erdin

2005

Phys. Rev. B

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Here we report a study of vortex states in a thin superconducting film with a magnetic dot grown upon it by means of a method based on London-Maxwell equations. Vortices with single quantum flux (Φ0 = hc/2e), giant vortices ( vortices with multiple flux ) as well as antivortices ( vortices with negative vorticity ) are taken into consideration. It turns out that giant vortices occur, when the dot's size is sufficiently smaller ( R ≤ 4.5ξ) than the effective penetration depth Λ. In the case of a dot with sufficiently large size ( R ≥ 6ξ ), the vortices with single quantum flux dominate the vortex states. Their geometrical patterns are predicted up to seven vortices. Our calculations do not show the spontaneous appearance of antivortices. PACS Number(s): 74.25. Dw, 74.25.Ha, 74.25.Qt, Type II superconductors are used in a wide variety of technological applications due to their high critical currents and fields [1]. In these superconductors, vortices appear when the magnetic field exceeds the first critical field H c1 . Under external current or field, vortices move, which causes the superconductor to switch to a resistive state. As a result, the system loses its superconductivity. Because of this, vortex pinning is quite important in applications of type II superconductors. One of the ways to pin vortices is to use the magnetic subsytems with either out-of-plane or in-plane magnetization. These subsystems are capable of trapping both vortices and antivortices, depending on the orientation and strength of their magnetization. The aforementioned systems are not only important for technological applications, such as devices that can be tuned by weak magnetic fields, but also offer rich physical effects which are not observed in the individual parts. Some of these effects were predicted elsewhere [2][3][4][5][6][7].In the recent decade, magnetic dots growing on top of SC films have been extensively studied both experimentally [8] and theoretically [9,10]. In experimental studies, magnetic dots with in-plane magnetization are fabricated from Co, Ni, Fe, Gd-Co and Sm-Co alloys, whereas, for the dots with magnetization perpendicular to the plane, Co/Pt multilayers are used [11]. These studies report commensurability effects on transport properties, which comfirm that the dots create and pin vortices. On theoretical side, several realizations of the aforementioned systems are analyzed through the Landau-Gizburg framework and London theory. In these works, the authors investigated the conditions for vortices to appear and calculated their geometric configurations in equilibrium.Recently, Priour et al. studied the vortex states of a SC film with a magnetic dot array grown upon on it, through Ginzburg-Landau theory, and found several different configurations of vortices in the SC film [12]. Similar study was also done by Peeters et al., but in the presence of a single dot [13,14]. One of the interesting results that is reported by these works is, when the dot's size is on the order of a few coherence lengths ξ, vortices with...

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