Magnetically pinned ring dots for spin valve or magnetic tunnel junction memory cells

Nakatani, Ryoichi; Yoshida, Tsuyoshi; Endo, Yasushi; Kawamura, Yoshio; Yamamoto, Masahiko; Takenaga, Takashi; Aya, Sunao; Kuroiwa, Takeharu; Beysen, Sadeh; Kobayashi, Hiroshi

doi:10.1016/j.jmmm.2004.09.031

Cited by 20 publications

(4 citation statements)

References 12 publications

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“…Recently, exchange bias has also been demonstrated to be an effective means for tailoring the magnetization reversal of elliptical dots [12]. Although there have been some reports on room temperature studies of multilayer ring structures consisting of metallic AFM layers such as IrMn or FeMn [13][14][15], to date there has been no work on the magnetic properties of exchange-biased rings incorporating oxide AFM layers such as CoO. Using CoO as the AFM layer is suitable due to its Néel temperature T N = 291 K, which is just below room temperature, thus enabling the exchange bias to be reset conveniently.…”

Section: Introductionmentioning

confidence: 99%

Controlling the magnetization reversal in exchange-biased Co/CoO elongated nanorings

et al. 2008

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We report on the control of magnetization reversal in exchange-biased Co/CoO nanorings resulting from the competition between field-cooling-induced unidirectional anisotropy at the Co/CoO interface and shape anisotropy of the elongated Co nanorings. We observed that the magnetization reversal mechanisms and magnitudes of exchange bias fields are strongly dependent on the strength and orientation of the cooling field relative to the major axis of the nanorings. Our results demonstrate a convenient technique to control the magnetization reversal modes in ferromagnetic nanorings.

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Section: Introductionmentioning

confidence: 99%

Controlling the magnetization reversal in exchange-biased Co/CoO elongated nanorings

et al. 2008

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“…As a source of unidirectional anisotropy, it has been shown that exchange bias ͑EB͒ can be used to control the reversal mechanisms in patterned nanomagnets. 17 While the majority of work on rings has been concerned with single layer, 16,18 or pseudospin valve structures, [19][20][21] there is limited reported work on EB bilayer rings [22][23][24] especially at low temperatures.…”

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confidence: 99%

Magnetic properties of exchange biased Co/CoO elongated nanoring arrays

Tripathy

Adeyeye

2009

Journal of Applied Physics

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We present a systematic study of the magnetic properties of exchange biased Co͑25 nm͒ / CoO͑t CoO ͒ / Cu͑2 nm͒ elongated nanoring arrays. The reversal mechanism in the exchange biased nanorings is directly compared to that of unbiased nanorings of identical geometry at varying temperatures. We observe that along the field cooling direction, the exchange biased nanorings exhibit reversal via shifted vortex states with enhanced magnitudes of onion→ vortex and vortex→ reverse onion transition fields. The magnitude of exchange bias field is also found to be strongly dependent on the CoO layer thickness t CoO , and decreases monotonically with increasing t CoO . Due to the interplay between the exchange and Zeeman energies, the exchange bias field could also be varied by adjusting the field cooling strength.There has been an emerging scientific interest in the magnetization reversal mechanisms of patterned nanomagnets with precisely controlled geometry and interelement spacing 1 due to potential applications in a wide range of magnetoelectronic devices such as magnetic random access memory, 2 read head sensors, 3 programmable logic devices, 4 and ultrahigh density patterned storage media. 5 From a fundamental viewpoint, nanomagnets offer by virtue of their low dimensionality, a wide range of magnetic properties which are not observed in their continuous bulk counterparts, especially when the size becomes comparable to or smaller than certain characteristic length scales such as spin diffusion length, carrier mean free path, and magnetic domain wall width. 6 Therefore, the influence of shape and size on the magnetic properties of square, 7-9 circular, 10,11 elliptical, 12,13 diamond, 14 and triangular 15 shaped nanomagnets has been widely investigated.Recently, a substantial amount of study has also been conducted on ring shaped nanomagnets driven by its technological importance and appealing magnetic states, namely, the flux-closure or "vortex" state in which the magnetization is oriented circumferentially around the ring, either clockwise or counterclockwise, and the bidomain or "onion" state in which two halves of the ring magnetization adopt opposite circulations, with each half separated by 180°domain walls. 16 For successful implementation in any magnetoelectronic device, it is imperative to achieve a consistent and experimentally tunable switching mechanism in such ring elements. As a source of unidirectional anisotropy, it has been shown that exchange bias ͑EB͒ can be used to control the reversal mechanisms in patterned nanomagnets. 17 While the majority of work on rings has been concerned with single layer, 16,18 or pseudospin valve structures, 19-21 there is limited reported work on EB bilayer rings 22-24 especially at low temperatures.In this work, a systematic study of the magnetic properties of EB Co/CoO elongated nanoring arrays is presented as a function of temperature. We observe that the magnetization reversal in nanorings is significantly modified due to EB. The evolution in EB field H E is also inves...

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“…The shape and size of a nanosized magnet markedly influence its behavior. 1,2) Because nanosized magnets are promising materials for practical applications, the magnetization reversal processes and domain wall configurations of nanosized magnets have been studied intensively, e.g., for nonvolatile memory devices, 3,4) magnetic storage media, 5) and magnetic logic gates. 6,7) In particular, magnetic nanowires are attractive as nanosized magnets from both fundamental and applied points of view [8][9][10][11] because inducing a magnetic field 10) or current 11) can control their domain wall motion.…”

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confidence: 99%

Observation of Magnetization Reversal Process in Ni–Fe Nanowire Using Magnetic Field Sweeping-Magnetic Force Microscopy

Endo

Matsumura

Fujimoto

et al. 2007

jjap

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The details of the magnetization reversal process of Ni–Fe nanowires, which were 10, 30, and 50-nm thick, were successfully observed using our newly proposed magnetization measurement method, namely, magnetic field sweeping (MFS)-magnetic force microscopy (MFM). All the points within the nanowire show marked phase changes (stray fields change) as the magnetic field is varied. In particular, each nanowire edge displays a hysteresis loop, while the center shows a sharp jump or a plateau area. These results demonstrate that domain wall motion is dominant in the magnetization reversal process of a 10-nm-thick Ni–Fe nanowire and that domain wall motion along with domain wall pinning play important roles in the magnetization reversal process in both 30- and 50-nm-thick Ni–Fe nanowires.

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Magnetically pinned ring dots for spin valve or magnetic tunnel junction memory cells

Cited by 20 publications

References 12 publications

Controlling the magnetization reversal in exchange-biased Co/CoO elongated nanorings

Controlling the magnetization reversal in exchange-biased Co/CoO elongated nanorings

Magnetic properties of exchange biased Co/CoO elongated nanoring arrays

Observation of Magnetization Reversal Process in Ni–Fe Nanowire Using Magnetic Field Sweeping-Magnetic Force Microscopy

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