Size dependence of magnetization reversal of ring shaped magnetic tunnel junction

Chen, C. C.; Kuo, Chao‐Yin; Chang, Y. C.; Chang, Chia‐Chi; Horng, Lance; Wu, Te‐Ho; Chern, G.; Huang, Ching-Yu; Tsunoda, Masakiyo; Takahashi, M.; Wu, Jong-Ching

doi:10.1016/j.jmmm.2006.10.686

Cited by 7 publications

(2 citation statements)

References 8 publications

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“…P ATTERNED trilayer ferromagnetic/nonmagnetic/ferromagnetic (F/N/F) systems are of fundamental interest due to the strong interactions between the magnetic layers, and have application in magnetic random access memory, magneto-electronic devices, and especially GMR multilayers [1], [2]. Interlayer magnetostatic coupling plays a significant role when the lateral size of the device is reduced [3], and both magnetostatic and exchange coupling affect the switching process and coercive field of the patterned F/N/F system, depending on the thickness and material of the spacer layer [4].…”

Section: Introductionmentioning

confidence: 99%

Effects of Interlayer Coupling in Elongated $\hbox{Ni}_{80}\hbox{Fe}_{20}/\hbox{Au/Co}$ Nanorings

et al. 2010

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We describe the magnetization reversal processes in multilayer elongated Ni 80 Fe 20 (10 nm) Au( = 0 to 20 nm) Co(20 nm) Si( 001) nanorings. For a field applied in-plane along the long axis, the hysteresis loops display a two-step switching for both = 0 nm and 2 nm, and a three-step switching for = 10 nm and 20 nm. Onion-to-vortex and vortex-to-reverse onion state transitions occur for a thin Au spacer due to strong exchange coupling between the layers. For a thick Au spacer layer, the Ni 80 Fe 20 layer switches first, then a two-step reversal of the Co, correlated with domain motion in the Ni 80 Fe 20 , occurs without the formation of vortex states as a result of magnetostatic interactions. There is a good agreement between the experimental results and micromagnetic simulations. Index Terms-Co Au Ni 80 Fe 20 , elongated nanorings, exchange coupling, MOKE.

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Section: Introductionmentioning

confidence: 99%

Effects of Interlayer Coupling in Elongated $\hbox{Ni}_{80}\hbox{Fe}_{20}/\hbox{Au/Co}$ Nanorings

et al. 2010

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“…The four distinct resistance levels associated with four magnetization configurations within the free layer are observed throughout the magnetization reversal process, which can be inferred to be onion, vortexpair, vortex, and reverse onion states, relative to the fixed quasi-uniform magnetization configuration of the pinned layer. 18) In addition, two discernable characteristics can be addressed in Fig. 3.…”

Section: Resultsmentioning

confidence: 99%

Effects of Field Cooling Direction on Magnetoresistance of Exchange-Biased Magnetic Tunnel Junction Rings

Chen

Kuo

Horng

et al. 2009

jjap

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We report an effect of field cooling direction on the magnetoresistance of ring-shaped magnetic tunnel junctions consisting of Ta 5/Cu 20/ Ta 5/NiFe 2/Cu 5/MnIr 10/CoFe 4/Al-N 1.5/CoFe 4/NiFe 20/Ta 5-cap (thickness in nm). The magnetoresistances were both enhanced, in comparison to the as-fabricated ring device, with field-cooling directions applied in the film plane as well as perpendicular to the film plane but with greater increase in the case of perpendicular-field-cooled. Many cycles of planar-and perpendicular-field-cooled alternately gave the same results. The greater enhancement of magnetoresistance is shown to be due to the formation of an onion like magnetization configuration in the pinned layer after perpendicular-field-cooled, resulting in a better relative magnetization alignment between the pinned layer and the free layer in the minor loop region. Magnetic force microscopy (MFM) was undertaken to reveal the uniform and onion like magnetization configurations in the pinned layer of ring devices with the same dimensions, but with layer structures of Ta 5/NiFe 2/Cu 5/MnIr 10/CoFe 4/Cu 1/Ta 1 (thickness in nm) for the planar-and perpendicular-field-cooled, respectively. In addition, size-dependent behavior was explored and the results show that the formation of onion like magnetization after perpendicularfield-cooled is associated with the strong shape anisotropy in the narrower linewidths of ring devices.

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Magnetic noise in MgO-based magnetic tunnel junction rings

Feng

Diao

Feng

et al. 2010

Applied Physics Letters

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Magnetization switching is investigated in ring-shaped MgO-based magnetic tunnel junctions with 168% tunneling magnetoresistance. Besides the forward and reverse onion states, two vortex states and several metastable states are observed for the ferromagnetic free layer. Electrical noise is used to characterize the low frequency magnetization dynamics; a stationary 1 / f noise spectrum is observed within each magnetic state but they are separated by noise peaks which show a 1 / f 2 spectrum that is associated with slow random telegraph fluctuations. In the 1 / f region, the normalized magnetic noise parameter, ␣ mag , is shown to be consistent with the fluctuation-dissipation theorem.

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Size dependence of magnetization reversal of ring shaped magnetic tunnel junction

Cited by 7 publications

References 8 publications

Effects of Interlayer Coupling in Elongated $\hbox{Ni}_{80}\hbox{Fe}_{20}/\hbox{Au/Co}$ Nanorings

Effects of Interlayer Coupling in Elongated $\hbox{Ni}_{80}\hbox{Fe}_{20}/\hbox{Au/Co}$ Nanorings

Effects of Field Cooling Direction on Magnetoresistance of Exchange-Biased Magnetic Tunnel Junction Rings

Magnetic noise in MgO-based magnetic tunnel junction rings

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