| 1. |
- Fisun, V. V., et al.
(författare)
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Features in nonlinear electroconductivity of nanocontacts on the base of ferromagnetic metals (Co and Fe)
- 2004
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Ingår i: Metallofizika i novejsie tehnologii. - 1024-1809. ; 26:11, s. 1439-1446
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Tidskriftsartikel (refereegranskat)abstract
- For normal metal-ferromagnet (N-F) point contacts, a step-like change of the resistance is observed at reaching of the current density similar to 10(9) A/cm(2). This is observed only for the case, when electron flow is directed from the normal metal to the ferromagnetic one, and is connected with magnetization reversal in the microconstriction at high transport-current density. Increasing of a magnetic field leads to the shift of observed peculiarity into the higher-current region that testifies its magnetic origin. As shown, the observed effect, which is widely studied in the recent time in N-F sandwiches, has more common character and requires the presence only N-F boundary and high-current density. The increasing of the amplitude of the resistance peculiarity is observed at electromagnetic radiation with a frequency of 3.10(9) Hz that testifies stimulating influence of the HF-radiation on the dynamics of precessing spins in the contacts at issue.
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| 2. |
- Gromov, A., et al.
(författare)
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Electromagnetic analysis of layered magnetic/conductor structures
- 2000
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 33:7, s. 773-779
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Tidskriftsartikel (refereegranskat)abstract
- A method is described for calculating the impedance of conductor structures comprised of ferromagnetic and non-magnetic layers of arbitrary cross sectional shape with transverse dimensions which are small compared to the conductors length. The method is exemplified on a conductor of axial symmetry enclosed in a high permeability film of uniaxial anisotropy along the conductor axis. To find the impedance the full boundary value problem for the vector potential is solved, allowing driving and eddy currents in both the conductor and the magnetic film, and taking into account the dynamics of the magnetization governed by the Landau-Lifshitz equations. The results obtained are used to model the giant magneto impedance effect in ferromagnetically coated wires.
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| 3. |
- Johansson, Jan, et al.
(författare)
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Giant fluctuations of superconducting order parameter in ferromagnet-superconductor single-electron transistors
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:21
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Tidskriftsartikel (refereegranskat)abstract
- Spin dependent transport in a ferromagnet-superconductor single-electron transistor is studied theoretically taking into account spin accumulation, spin relaxation, gap suppression, and charging effects. A strong dependence of the gap on the magnetic state of the electrodes is found, which gives rise to a magnetoresistance of up to 100%. We predict that fluctuations of the spin accumulation can play such an important role as to cause the island to fluctuate between the superconducting and normal states. Furthermore, the device exhibits a nearly complete gate-controlled spin-valve effect.
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| 4. |
- Johansson, Jan, et al.
(författare)
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Suppression of superconductivity due to spin imbalance in Co/Al/Co single electron transistor
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93, s. 8650-8652
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Tidskriftsartikel (refereegranskat)abstract
- Transport properties of ferromagnetic/nonmagnetic/ferromagnetic single electron transistors are investigated as a function of external magnetic-field, temperature, bias, and gate voltage. By designing the magnetic electrodes to have different switching fields, a two-mode device is realized having two stable magnetization states, with the electrodes aligned in parallel and antiparallel. Magnetoresistance of approximately 100% is measured in Co/AlOX/Al/AlOX/Co double tunnel junction spin valves at low bias, with the Al spacer in the superconducting state. The effect is substantially reduced at high bias and temperatures above the T-C of the Al. The experimental results are interpreted as due to spin imbalance of charge carriers resulting in suppression of the superconducting gap of the Al island.
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| 5. |
- Korenivski, Vladislav
(författare)
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GHz magnetic film inductors
- 2000
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Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 215, s. 800-806
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Tidskriftsartikel (refereegranskat)abstract
- Use of magnetic films for miniaturization of planar inductors operating at ultra-high frequencies is reviewed. Materials and design aspects determining the efficiency of the devices are analyzed. Mechanisms involved in magnetic dissipation and their role in limiting the device operation frequency range and quality factor are discussed. Typical inductor geometries are considered. A magnetically sandwiched strip inductor is argued to hold a promise for GHz applications.
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| 6. |
- Sukstanskii, A., et al.
(författare)
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Impedance of a ferromagnetic sandwich strip
- 2001
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 89:1, s. 775-782
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical approach for calculating the impedance of a three-layer sandwich, consisting of two metallic ferromagnetic layers separated by a non-magnetic conductive layer, is presented. The Maxwell equations for the electromagnetic field coupled with the Landau-Lifshitz equations for the magnetization dynamics are solved, which enables one to describe the system over a wide frequency range, including the ferromagnetic resonance. Two sandwich strip structures are analyzed, both having thickness much less than the width, and the width much less than the length: a closed structure with the magnetic film closing at the edges along the width, and an open structure without flux closures where all the layers have the same width. The impedance for the two structures is calculated and analyzed as a function of the physical parameters of the device and frequency. The closed structure is more efficient magnetically and exhibits a highly inductive response to much higher frequencies than the open structure. The analytical results obtained are directly applicable to practical design of GHz inductive components.
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| 7. |
- Sukstanskii, A. L., et al.
(författare)
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Impedance and surface impedance of ferromagnetic multilayers : the role of exchange interaction
- 2001
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 34:23, s. 3337-3348
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Tidskriftsartikel (refereegranskat)abstract
- A theory of impedance and surface impedance in conductive ferromagnetic films and layered magnetic/conductor structures is presented. The theory is based on solving Maxwell's equations for the magnetic and electric fields and the Landau-Lifshitz equations for the magnetization. The exchange interaction in the magnetic films as well as pinning at surfaces are taken into account. The analytical results obtained demonstrate the importance of the exchange, pinning and also the type of excitation the magnetic systems are subject to in describing their properties at ultrahigh frequencies.
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| 8. |
- Sukstanskii, A., et al.
(författare)
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Magnetostatic spin waves in metallic multilayers
- 2000
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Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 218:03-feb, s. 144-150
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Tidskriftsartikel (refereegranskat)abstract
- Magnetostatic spin waves in a multilayer film consisting of two magnetic conductive layers separated by a nonmagnetic conductor are analyzed. Two magnetostatic spin wave branches are shown to exist and their dispesion laws are analyzed. Structures of finite width, which are relevant for device applications, are also considered.
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| 9. |
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| 10. |
- Urech, Mattias, et al.
(författare)
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Magnetic switching and magnetoresistance in nanoscale spin tunnel junctions
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:10, s. 6062-6065
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Tidskriftsartikel (refereegranskat)abstract
- Co/AlOx/Co magnetic tunnel junctions in both multijunction arrays and double-tunnel junction geometries have been studied. The junctions exhibit magnetoresistance (MR) and change their resistance by similar to10% depending on the relative magnetic orientation of the tunnel junction electrodes. MR measurements show a strong dependence on the device geometry. We find that it is necessary to form tunnel junctions with electrode width similar to70 nm for the magnetic switching at the tunnel junction to be clean and single domain like.
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