Extraordinary Hall effect in magnetic films

Gerber, A.; Milner, A.; Karpovsky, Mark G.; Lemke, Benjamin; Habermeier, H.‐U.; Tuaillon-Combes, J.; Négrier, M.; Boisron, Olivier; Mélinon, P.; Pérez, A.

doi:10.1016/s0304-8853(01)01207-0

Cited by 60 publications

(31 citation statements)

References 30 publications

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“…The current sensitivity S I is about 0.9 V / AT in the linear region ͑i.e., below 1 T͒. Since the device thickness is about 50 nm, this corresponds to a Hall coefficient R H of about 5 ϫ 10 −8 ⍀ m/T ͑similar to that reported for Fe-Pt, Fe-Si, Ni, and LaBaMnO 3 thin films, [10][11][12][13][14][15] and Fe-Cr multilayers 16 ͒. The resistance between the bias current contacts varies by less than 0.5% from 0 to 2.2 T. At magnetic inductions higher than 1 T, the Hall voltage saturates ͑above 1 T the Hall voltage varies by only a few microvolts͒.…”

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confidence: 98%

“…5 Magnetic materials show additional "Hall phenomena" which are, generally speaking, generated by spin-orbit interactions: the so-called extraordinary [10][11][12][13][14][15][16] and planar Hall effects.…”

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confidence: 99%

“…[4][5][6][7][8][9] The ordinary Hall effect is due to the Lorentz force acting on charge carriers in metals, semi-metals, and semiconductors. 5 Magnetic materials show additional "Hall phenomena" which are, generally speaking, generated by spin-orbit interactions: the so-called extraordinary [10][11][12][13][14][15][16] and planar Hall effects. [17][18][19][20] The local deposition of materials using a focused electron beam in the presence of a volatile precursor is a wellestablished technique for the maskless fabrication of submicrometer structures such as functionalized tips for scanning probe microscopy, [21][22][23][24][25][26] electrodes for local conductivity measurements, 27 solder bonds for carbon nanotubes studies, 28 nanowires, [29][30][31][32][33] and nanodots.…”

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Submicrometer Hall devices fabricated by focused electron-beam-induced deposition

et al. 2005

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Hall devices having an active area of about ͑500 nm͒ 2 are fabricated by focused electron-beam-induced deposition. The deposited material consists of cobalt nanoparticles in a carbonaceous matrix. The realized devices have, at room temperature, a current sensitivity of about 1 V / AT, a resistance of a few kilo-ohms, and can be biased with a maximum current of about 1 mA. The room-temperature magnetic field resolution is about 10 T/Hz 1/2 at frequencies above 1 kHz. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1856134͔Magnetic sensors having submicrometer spatial resolution are key elements in several fundamental studies as well as industrial applications.1-4 Hall effect devices are emerging as one of the most suitable solutions. [4][5][6][7][8][9] The ordinary Hall effect is due to the Lorentz force acting on charge carriers in metals, semi-metals, and semiconductors.5 Magnetic materials show additional "Hall phenomena" which are, generally speaking, generated by spin-orbit interactions: the so-called extraordinary [10][11][12][13][14][15][16] and planar Hall effects. 17-20The local deposition of materials using a focused electron beam in the presence of a volatile precursor is a wellestablished technique for the maskless fabrication of submicrometer structures such as functionalized tips for scanning probe microscopy, 21-26 electrodes for local conductivity measurements, 27 solder bonds for carbon nanotubes studies, 28 nanowires, 29-33 and nanodots. 34 In this letter we demonstrate the possibility to grow highly sensitive cobaltcarbon submicrometer Hall devices by means of a focused electron beam. This flexible "single-step" process represents an alternative to the conventional "multisteps" methods, which are usually based on a combination of optical ͑or electron beam͒ lithography and focused ion beam milling. The realized devices show a strong extraordinary Hall effect, whereas the ordinary and planar Hall effects ͑in most of the devices͒ are relatively small.

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Submicrometer Hall devices fabricated by focused electron-beam-induced deposition

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“…R OH is found from measuring V H in fields beyond the sample's magnetic saturation, and can then be used to subtract the term linear in B Z from Eq. (1), producing a signal directly proportional to the sample's magnetization M Z :The technique was shown [12,13] Results and discussion I. Cumulative minor loops where M s is the saturated magnetization, V EHE is extracted by using Eq.…”

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Dynamics of successive minor hysteresis loops

2012

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Cumulative growth of successive minor hysteresis loops in Co/Pd multilayers with perpendicular anisotropy was studied in the context of time dependent magnetization reversal dynamics. We show that in disordered ferromagnets, where magnetization reversal involves nucleation, domains' expansion and annihilation, differences between the time dependencies of these processes are responsible for accumulation of nuclei for rapid domain expansion, for the asymmetry of forward and backward magnetization reversals and for the respective cumulative growth of hysteresis loops. Loops stop changing and become macroscopically reproducible when populations of upward and downward nucleation domains balance each other and the respective upward and downward reversal times stabilize. PACS: 75.60.Jk, 75.70.Cn, IntroductionReproducibility of cycling processes under identical external conditions attracts particular attention in studies of magnetic hysteresis for at least two reasons: the effect is fundamental to all magnetic storage technologies, and it can serve as a model for a wide range of type-I phase transitions. Two types of hysteresis loops are distinguished."Major" loops are obtained by sweeping the applied field beyond the saturation field H sat , above which the system is said to be fully saturated and its magnetization M(H) is a single-valued function of the applied field H; "minor" loops are obtained when the cycle is limited to fields near and below H sat . Many studies were devoted to the macroscopic and microscopic repeatability of minor and major hysteresis loops and effects of disorder on cycle-to-cycle memory [1,2]. Macroscopically the major loops repeat themselves in successive cycles, however it was appreciated [3,4] that disorder induces memory in the microscopic magnetic domain configurations from one cycle of the hysteresis loop to the next, even when H sat was crossed. Successive minor loops are usually reasonably reproducible, although changes of size and shape were observed [5][6][7]. Nevertheless these finite perturbations did not undermine a generally accepted view that macroscopic hysteresis loops are repeatable. It came therefore as a surprise when Berger et al. [8] reported major cumulative expansion of successive minor hysteresis loops in Co/Pt and Co/Pd multilayers even up to four times their initial area. The phenomenon was explained in terms of successive accumulation of small nucleation domains, i.e. microscopic areas of reversed magnetization that act as nuclei for the subsequent macroscopic magnetization reversal [8,9]. The reversals at all but the first cycle do not start anew from a fully saturated state but from a preconfigured state in which nuclei for domain expansion are locally conserved. Conservation and accumulation of the nuclei can happen if the system responds asymmetrically in forward and reverse field orientations such that small domains appear to be substantially more stable toward annihilation in an opposite field than toward expansion in a forward field.In this paper we shall de...

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“…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.…”

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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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Extraordinary Hall effect in magnetic films

Cited by 60 publications

References 30 publications

Submicrometer Hall devices fabricated by focused electron-beam-induced deposition

Submicrometer Hall devices fabricated by focused electron-beam-induced deposition

Dynamics of successive minor hysteresis loops

Perspective of Spintronics Applications Based on the Extraordinary Hall Effect

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