| 1. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Thermoelectrical manipulation of nano-magnets : A spin-thermionic oscillator
- 2010
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - San Diego, CA : SPIE. - 9780819482563 ; 7760, s. 77600R-1 - 77600R-17-
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Konferensbidrag (refereegranskat)abstract
- We investigate the interplay between the thermodynamic properties and spin-dependent transport in a mesoscopic magnetic multilayer, in which two strongly ferromagnetic layers are exchange-coupled through a weakly ferromagnetic spacer. We show theoretically that the system allows a spin-thermoelectronic control of the relative orientation of the outer layers. Supporting experimental evidence of thermally controlled switching from parallel to anti-parallel magnetization orientations in the sandwich is presented. We show magneto-resistance oscillations may take place with frequencies up to GHz. We discuss in detail an experimental realization of a device that can operate as a thermo-magneto-resistive switch or oscillator.
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| 2. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Thermoelectrical manipulation of nanomagnets
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 107:12, s. 123706-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the interplay between the thermodynamic properties and spin-dependent transport in a mesoscopic device based on a magnetic multilayer (F/f/F), in which two strongly ferromagnetic layers (F) are exchange-coupled through a weakly ferromagnetic spacer (f) with the Curie temperature in the vicinity of room temperature. We show theoretically that the Joule heating produced by the spin-dependent current allows a spin-thermoelectronic control of the ferromagnetic-to-paramagnetic (f/N) transition in the spacer and, thereby, of the relative orientation of the outer F-layers in the device (spin-thermoelectric manipulation of nanomagnets). Supporting experimental evidence of such thermally-controlled switching from parallel to antiparallel magnetization orientations in F/f(N)/F sandwiches is presented. Furthermore, we show theoretically that local Joule heating due to a high concentration of current in a magnetic point contact or a nanopillar can be used to reversibly drive the weakly ferromagnetic spacer through its Curie point and thereby exchange couple and decouple the two strongly ferromagnetic F-layers. For the devices designed to have an antiparallel ground state above the Curie point of the spacer, the associated spin-thermionic parallel to antiparallel switching causes magnetoresistance oscillations whose frequency can be controlled by proper biasing from essentially dc to GHz. We discuss in detail an experimental realization of a device that can operate as a thermomagnetoresistive switch or oscillator.
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| 3. |
- Nordenfelt, Anders, et al.
(författare)
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Magnetomotive Instability and Generation of Mechanical Vibrations in Suspended Semiconducting Carbon Nanotubes
- 2010
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the electromechanics of a freely suspended semiconducting carbon nanotube subjected to a magnetic field H in the current-biased regime and show that self-excitation of mechanical nanotube vibrations can occur if H exceeds a critical value Hc of the order of 10–100 mT. The effect can be detected by measuring the magnetic field dependence of the time-averaged voltage drop across the nanotube, which has a singularity at H=Hc. We discuss the applications of the device as an active, tuneable radiofrequency oscillator.
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| 4. |
- Radic, Danko, 1970, et al.
(författare)
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Self-excited oscillations of charge-spin accumulation due to single-electron tunneling
- 2010
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Ingår i: Physical Review B. - 1098-0121. ; 82:12, s. 125311 (7 pages)-
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically study electronic transport through a layer of quantum dots connecting two metallic leads. By the inclusion of an inductor in series with the junction, we show that steady electronic transport in such a system may be unstable with respect to temporal oscillations caused by an interplay between the Coulomb blockade of tunneling and spin accumulation in the dots. When this instability occurs, a new stable regime is reached, where the average spin and charge in the dots oscillate periodically in time. The frequency of these oscillations is typically on the order of 1 GHz for realistic values of the junction parameters.
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| 5. |
- Sonne, Gustav, 1982, et al.
(författare)
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Cooling of a suspended nanowire by an ac Josephson current flow
- 2010
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 104:22
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Tidskriftsartikel (refereegranskat)abstract
- We consider a nanoelectromechanical Josephson junction, where a suspended nanowire serves as a superconducting weak link, and show that an applied dc bias voltage can result in suppression of the flexural vibrations of the wire. This cooling effect is achieved through the transfer of vibronic energy quanta first to voltage-driven Andreev states and then to extended quasiparticle electronic states. Our analysis, which is performed for a nanowire in the form of a metallic carbon nanotube and in the framework of the density matrix formalism, shows that such self-cooling is possible down to the ground state of the flexural vibration mode of the nanowire.
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| 6. |
- Sonne, Gustav, 1982, et al.
(författare)
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Voltage-driven superconducting weak link as a refrigerator for cooling of nanomechanical vibrations
- 2010
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1090-6517 .- 1063-777X. ; 36:10
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Tidskriftsartikel (refereegranskat)abstract
- We consider a new type of cooling mechanism for a suspended nanowire acting as a weak link between two superconductive electrodes. By applying a bias voltage over the system, we show that the system can be viewed as a refrigerator for the nanomechanical vibrations, where energy is continuously transferred from the vibrational degrees of freedom to the extended quasiparticle states in the leads through the periodic modulation of the inter-Andreev level separation. The necessary coupling between the electronic and mechanical degrees of freedom responsible for this energy-transfer can be achieved both with an external magnetic or electrical field, and is shown to lead to an effective cooling of the vibrating nanowire. Using realistic parameters for a suspended nanowire in the form of a metallic carbon nanotube we analyze the evolution of the density matrix and demonstrate the possibility to cool the system down to a stationary vibron population of ~0.1. Furthermore, it is shown that the stationary occupancy of the vibrational modes of the nanowire can be directly probed from the dc current responsible for carrying away the absorbed energy from the vibrating nanowire.
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