| 1. |
- Balkashin, O. P., et al.
(författare)
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Ferromagnetic resonance in copper-permalloy point contacts
- 2014
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Ingår i: Fizika Nizkih Temperatur. - 0132-6414 .- 1816-0328. ; 40:10, s. 1187-1197
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Tidskriftsartikel (refereegranskat)abstract
- The systematic investigations of the response signal of Copper-Permalloy (Ni80Fe20) point contacts to microwave irradiation (8-12 GHz) are performed. The influence of external magnetic field strength, transport current flowing through the contact, the intensity and frequency of the RF exposure on the measured signal is studied. The contributions to the contacts resistance from the effects of giant and anisotropic magnetoresistance are analyzed. It is established experimentally that the position of resonance features is in good agreement with the Kittel formula calculation for FMR in the film at a parallel H field. The resonance signal was observed on the background of an additional contribution due to the rectification of RF current on the nonlinear contact IV-curve. It is found that there are two mechanisms for the resonant response are revealed: a synchronous self-detection by means of mixing of RF current with temporal variations of resistance and a bolometric mechanism associated with a steady-state change of contact resistance under excitation of magnetization precession (a bolometric response). It is found that the resonance signal amplitude is linearly proportional to transport current through the contact and microwave irradiation intensity.
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| 2. |
- Balkashin, O. P., et al.
(författare)
-
Ferromagnetic resonance in copper-permalloy point contacts
- 2014
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 40:10, s. 929-936
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Tidskriftsartikel (refereegranskat)abstract
- The response of copper-permalloy (Ni80Fe20) point microcontacts to microwave irradiation (8-12 GHz) is investigated systematically. The effects of the external magnetic field strength, transport current flowing through the contact, and microwave intensity and frequency on the measured signal are studied. The contributions to the contact electrical resistance owing to giant and anisotropic magnetoresistance are analyzed. The experimentally determined positions of the resonance features are in good agreement with Kittel's formula for FMR in films in parallel magnetic fields. The resonance signal is observed against the background of an additional contribution owing to rectification of the rf field on the nonlinear current-voltage characteristic of the contact. Two mechanisms for the resonance response are discovered: synchronous self-detection from mixing of the rf current with temporal variations in the resistance and a bolometric response associated with the steady-state variation in the contact resistance when magnetization precession is excited. The amplitude of the resonance signal is linearly proportional to the transport current through the contact and to the intensity of the microwave irradiation.
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| 3. |
- Balkashin, O. P., et al.
(författare)
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Nonstationary magnetization dynamics of point contacts with a single ferromagnetic film
- 2009
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 35:8-9, s. 693-701
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Tidskriftsartikel (refereegranskat)abstract
- The electric conductivity of point nanocontacts between 5, 10, and 100 nm thick ferromagnetic (F) cobalt films and a nonmagnetic (N) metal (copper or silver) needle is investigated. Two fundamentally different mechanisms for the formation of the response, signal to microwave irradiation have been observed for the first time. One mechanism is due to the effect of the rectification of high frequency ac current on the nonlinearity of the current-voltage characteristics due to the precession of the magnetization under the action of a constant transport current flowing through the contact. The second one is associated with the resonance excitation of the precession of the magnetization vector at the fundamental frequency and its harmonic by an external high-frequency field. The experimental results support a previous contention that a "surface spin valve" whose static and dynamic properties are similar to conventional F-1-N-F-2 spin valve [Nano Letters 7, 927 (2007)] is formed in the experimental F-N nanocontacts.
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| 4. |
- Balkashin, O. P., et al.
(författare)
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Spin dynamics in point contacts to single ferromagnetic films
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:9, s. 092419-1-092419-4
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Tidskriftsartikel (refereegranskat)abstract
- Excitation of magnons or spin waves driven by nominally unpolarized transport currents in point contacts of normal and ferromagnetic metals is probed by irradiating the contacts with microwaves. Two characteristic dynamic effects are observed: a suppression of spin-wave nonlinearities in the point contact conductance by off-resonance microwave irradiation and a resonant stimulation of spin-wave peaks in the differential resistance of the nanocontacts by the microwave field. These observations provide direct evidence that the magnetoresistance peaks observed are due to gigahertz spin dynamics at the ferromagnetic interface driven by the spin transfer torque effect of the transport current.
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| 5. |
- Balkashin, O. P., et al.
(författare)
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Spin-valve effects in point contacts to exchange biased Co40Fe40B20 films
- 2014
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 40:10, s. 915-918
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear current-voltage characteristics and magnetoresistance of point contacts between a normal metal (N) and films of amorphous ferromagnet (F) Co40Fe40B20 of different thickness, exchange-biased by antiferromagnetic Mn80Ir20 are studied. A surface spin valve effect in the conductance of such F-N contacts is observed. The effect of exchange bias is found to be inversely proportional to the Co40Fe40B20 film thickness. This behavior as well as other magneto-transport effects we observe on single exchange-pinned ferromagnetic films are similar in nature to those found in conventional three-layer spin-valves.
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| 6. |
- Balkashin, O. P., et al.
(författare)
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Spin-valve effects in point contacts to exchange biased Сo 40Fe 40B 20 films
- 2014
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Ingår i: Fizika Nizkih Temperatur. - 0132-6414 .- 1816-0328. ; 40:10, s. 1170-1174
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear current-voltage characteristics and magnetoresistance of point contacts between a normal metal (N) and films of amorphous ferromagnet (F) Co40Fe40B20 of different thickness, exchange-biased by antiferromagnetic Mn80Ir20 are studied. A surface spin valve effect in the conductance of such F-N contacts is observed. The effect of exchange bias is found to be inversely proportional to the Co40Fe40B20 film thickness. This behavior as well as other magneto-transport effects we observe on single exchange-pinned ferromagnetic films are similar in nature to those found in conventional three-layer spin-valves.
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| 7. |
- 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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| 8. |
- Kadigrobov, Anatoli M., 1937, et al.
(författare)
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Hot electrons in magnetic point contacts as a photon source
- 2011
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- We propose to use a point contact between a ferromagnetic and a normal metal in the presence of a magnetic field for creating a large inverted spin population of hot electrons in the contact core. The key point of the proposal is that when these hot electrons relax by flipping their spin, microwave photons are emitted, with a frequency tunable by the applied magnetic field. While point contacts are an established technology, their use as a photon source is a new and potentially very useful application. We show that this photon emission process can be detected by means of transport spectroscopy and demonstrate stimulated emission of radiation in the 10–100 GHz range for a model point contact system using a minority-spin ferromagnetic injector. These results can potentially lead to new types of lasers based on spin injection in metals.
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| 9. |
- Konovalenko, Alexander, et al.
(författare)
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On the mechanism of hysteresis in conductance of point contacts to single ferromagnetic films
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:9, s. 09A513-1-09A513-3
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Tidskriftsartikel (refereegranskat)abstract
- Single nonmagnetic/ferromagnetic interfaces can exhibit magnetic excitations and hysteretic switching, provided that the current density traversing the interface is sufficiently high (greater than or similar to 10(8) A/cm(2)) and the flow regime is diffusive. We measure hysteretic switching in conductance induced by nominally unpolarized electron currents in nanocontacts to thin Co films and successfully model the effect for similar to 20 nm scale point contacts using micromagnetic simulations, which take into account an out of plane stress-induced magnetic anisotropy in the point contact region.
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| 10. |
- Naidyuk, Yu G., et al.
(författare)
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Magnetic unipolar features in conductivity of point contacts between normal and ferromagnetic D-metals (Co, Ni, Fe)
- 2007
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Ingår i: Electron Correlation in New Materials and Nanosystems. - 9781402056574 ; , s. 59-69
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Konferensbidrag (refereegranskat)abstract
- In nanocontacts between normal and ferromagnetic metals (N-F) abrupt changes of the order of 1 % are detected in differential resistance, dV/dI(V), versus bias voltage, V, on achieving of high current densities, 10(9) A/cm(2). These features in dV/dI(V) are observed when the electron flow is directed from the nonmagnetic metal into the ferromagnet and connected with magnetization excitations in the ferromagnet induced by the current. Applying an external magnetic field leads to a shift of the observed features to higher biasing current, confirming the magnetic nature of the effect. Such effects are observed for the non-ballistic (not spectral) regime of current flow in the nanocontacts. Thus, the current induced magneto-conductance effects in multilayered N-F structures (nanopillars) extensively studied in the recent literature have much more general character and can be stimulated by elastic electron scattering at single N-F interfaces.
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