Size effect relating to the extraordinary and the ordinary Hall effect in ultrathin Fe-Pt films

Матвеев, В. Н.; Levashov, V. I.; Кононенко, О. В.; Чайка, А. Н.

doi:10.1134/s1063739706060072

Cited by 7 publications

(6 citation statements)

References 3 publications

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“…Longitudinal resistivity ρ and Hall resistivity ρ H of a series of Ni films are shown in Fig. Similar results were found in Co monolayers, Co-Pd bilayers [24], Fe-Pt films [25] and Fe/Ge multilayers [26]. Fig.…”

Section: Enhancement Of Sensitivity By Surface Scatteringsupporting

confidence: 78%

“…Longitudinal resistivity ρ and Hall resistivity ρ H of a series of Ni films are shown in Similar results were found in Co monolayers, Co-Pd bilayers [24], Fe-Pt films [25] and Fe/Ge multilayers [26]. Fig.3 presents the room temperature field sensitivity of polycrystalline Ni films as a function of their thickness.…”

Section: Enhancement Of Sensitivity By Surface Scatteringsupporting

confidence: 69%

“…Increase of sensitivity from 20 mΩ/T in 100 nm thick film to 30 Ω/T in 3 nm thick film is due both to the reduction of the thickness t and to the increase of the EHE resistivity in the thin film limit. Enhanced EHE resistivity and field sensitivity is a general property of ultrathin ferromagnetic materials observed also in CoFe/Pt multilayers [27], thin amorphous Fe-Ge [28] and ultrathin Fe-Pt films [25].…”

Section: Enhancement Of Sensitivity By Surface Scatteringmentioning

confidence: 88%

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Perspective of Spintronics Applications Based on the Extraordinary Hall Effect

Gerber¹,

Riss²

2008

Journal of Nanoelectronics and Optoelectronics

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Extraordinary Hall effect (EHE) is a spin-dependent phenomenon that generates voltageproportional to magnetization across a current carrying magnetic film. Magnitude of the effect can be artificially increased by stimulating properly selected spin-orbit scattering events. Already achieved sensitivity of the EHE-based sample devices exceeds 1000 Ω/T, which surpasses the sensitivity of semiconducting Hall sensors. Linear field response, thermal stability, high frequency operation, sub-micron dimensions and, above all, simplicity, robustness and low cost manufacture are good reasons to consider a wide scale technological application of the phenomenon for magnetic sensors and memory devices.2 Anisotropic magnetoresistance [1,2], planar Hall effect [3,4], spin-dependent tunneling [5,6] and the extraordinary or anomalous Hall effect (EHE) [7,8] are spin-dependent electronic transport phenomena known for many years. However, it is the discovery of the giant magnetoresistance (GMR) [9,10] that gave birth to the term spintronics and triggered a world-wide outburst of the spin-related research. Extraordinary Hall Effect (EHE) in magnetic materials was discovered more than a century ago [7], extensively studied both theoretically and experimentally [8], and left out of the mainstream research for the last thirty years. The possibility to use the effect for technical applications, such as magnetic sensors and nonvolatile magnetic random access memories (MRAM), has been mentioned more than three decades ago [11], but no significant progress was reported until recently. A probable reason for this is that although EHE in bulk magnetic materials can be significantly higher than the ordinary Hall effect in normal metals, its magnitude remained far beyond the sensitivity of semiconductors and magnetic sensors based on the anisotropic magnetoresistance [12]. The renewed interest in EHE has only recently arisen when some recipes to enhance the effect were found [13][14][15].The Hall effect in magnetic materials is commonly described [8,16] by the phenomenological equationwhere ρ H is the Hall resistivity, B, H and M are components of the magnetic induction, applied field and magnetization normal to the film plane, and D is the demagnetization factor. R 0 is the ordinary Hall coefficient related to the Lorentz force acting on moving charge carriers. R EHE , the extraordinary Hall coefficient, is associated with a break of the right-left symmetry at spin-orbit scattering in magnetic materials.. Demagnetization factor D is equal to 1 when field is applied perpendicular to a homogeneous magnetic film. In this case Eq.1 is simplified toVoltage measured between Hall contacts located perpendicular to the direction of an electric current is given by:where I is current and t thickness of the film. Fig.1 presents a typical field dependence of the Hall resistance (in a 4 nm thick Ni film at room temperature with field applied normal to the film plane.Magnetization normal to the film increases with field till saturation at about ±0.2 T. The EH...

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Section: Enhancement Of Sensitivity By Surface Scatteringsupporting

confidence: 78%

Section: Enhancement Of Sensitivity By Surface Scatteringsupporting

confidence: 69%

Section: Enhancement Of Sensitivity By Surface Scatteringmentioning

confidence: 88%

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Perspective of Spintronics Applications Based on the Extraordinary Hall Effect

Gerber¹,

Riss²

2008

Journal of Nanoelectronics and Optoelectronics

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“…The addition of insulating impurities into bulk transition metals [2] or the increase of surface scattering by reducing the thickness of magnetic films below the mean free path [3] can enhance the effect by orders of magnitude. Thin films of ordinary transition metals (Ni, Co, Fe) with dominant surface scattering were shown to reach EHE resistivity of the order of 1 µΩcm [1], whereas ultrathin alloys of FePt [4] and CoFe/Pt multilayers [5] reach the values of about 5 µΩcm.…”

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confidence: 99%

Reversal of the extraordinary Hall effect polarity in thin Co/Pd multilayers

Rosenblatt

Karpovski

Gerber

2010

Applied Physics Letters

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Ramat Aviv, 69978 Tel Aviv Israel Thin Co/Pd multilayers, with room temperature perpendicular anisotropy and an enhanced surface scattering, were studied for the possible use in the extraordinary Hall effect (EHE) -based magnetic memory devices. Polarity of the EHE signal was found to change from negative in thick samples to positive in thin ones. Reversal of EHE sign was also observed in thick samples with aging. The effect is argued to be related to the dominance of surface scattering having the EHE polarity opposite to that of the bulk. PACS: 73.50.-h, 75.50.Ss, 75.70.Cn Extraordinary or anomalous Hall effect (EHE) was discovered about 130 years ago, however, discussion of its practical application only started recently when it was demonstrated [1] that a relatively small EHE coefficient of bulk ferromagnets can be boosted by stimulating proper scattering events. The addition of insulating impurities into bulk transition metals [2] or the increase of surface scattering by reducing the thickness of magnetic films below the mean free path [3] can enhance the effect by orders of magnitude. Thin films of ordinary transition metals (Ni, Co, Fe) with dominant surface scattering were shown to reach EHE resistivity of the order of 1 µΩcm [1], whereas ultrathin alloys of FePt [4] and CoFe/Pt multilayers [5] reach the values of about 5 µΩcm.Tuning the perpendicular anisotropy in CoFe/Pt multilayers, and thus reducing the magnetic saturation field below the typical demagnetizing value, was shown to provide the field sensitivity exceeding 10 3 Ω/T [5] which competes with the best semiconducting Hall sensors. Use of the EHE for magnetic memory devices with a direct data read-out is another potential application. Combination of an out-of-plane anisotropy with a strong remanent EHE signal has been demonstrated in thin Ni films [1,6] at low temperatures.The goal of this work was the exploration of thin Co/Pd multilayers with room temperature perpendicular anisotropy in the thickness limit in which surface scattering can boost the magnitude of EHE, similar to the chemically homogeneous thin films. We shall demonstrate that the generation of room temperature magnetic memory units, and respectively, the magnetic random access memory based on the extraordinary Hall effect, is feasible. However, probably the most interesting and unexpected result we report on is the thickness and aging dependence of the EHE polarity in thin Co/Pd multilayers.

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“…In this case the saturable EHE is of the same order as the non-saturable OHE contribution. 56 With increasing temperature, the coercivity rapidly decreases and vanishes at T f ≃ 7 K for the film with 13 at.% of Ni and T f ≃ 12.8 K for 27 at.% of Ni. However, R xy (H) remains nonlinear, see curves with open circles in the main panels of Fig.…”

Section: Resultsmentioning

confidence: 92%

Anomalous Hall effect in NiPt thin films

Golod

Rydh

Krasnov

2011

Journal of Applied Physics

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We study Hall effect in sputtered NixPt1-x thin films with different Ni concentrations. Temperature, magnetic field and angular dependencies are analyzed and the phase diagram of NiPt thin films is obtained. It is found that films with sub-critical Ni concentration exhibit cluster-glass behavior at low temperatures with a perpendicular magnetic anisotropy below the freezing temperature. Films with over-critical Ni concentration are ferromagnetic with parallel anisotropy. At the critical concentration the state of the film is strongly frustrated. Such films demonstrate canted magnetization with the easy axis rotating as a function of temperature. The magnetism appears via consecutive paramagnetic - cluster glass - ferromagnetic transitions, rather than a single second-order phase transition. But most remarkably, the extraordinary Hall effect changes sign at the critical concentration. We suggest that this is associated with a reconstruction of the electronic structure of the alloy at the normal metal - ferromagnet quantum phase transition.Comment: 12 pages, 17 figure

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Size effect relating to the extraordinary and the ordinary Hall effect in ultrathin Fe-Pt films

Cited by 7 publications

References 3 publications

Perspective of Spintronics Applications Based on the Extraordinary Hall Effect

Perspective of Spintronics Applications Based on the Extraordinary Hall Effect

Reversal of the extraordinary Hall effect polarity in thin Co/Pd multilayers

Anomalous Hall effect in NiPt thin films

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