Suppression of Switching-Field Variation by Surface Oxidation Depending on the Shape of the CoFeB Free Layer

Takenaga, Takashi; Kuroiwa, Takeharu; Tsuchimoto, J.; Matsuda, Ryotaro; Ueno, Shinji; Takada, Hiroshi; Abe, Yoshitsugu; Tokuda, Yasunori

doi:10.1109/tmag.2007.893527

Cited by 5 publications

(4 citation statements)

References 9 publications

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“…Previous studies on CoFeB have shown the presence of a superparamagnetic layer, albeit generally with a smaller thickness ͑ranging from 3 to 8.5 Å, depending on the adjacent layers͒. 13,14 Our study suggests a more complicated scenario. As we increase the thickness of CoFeB, sputter deposition yields the formation of discrete clusters of CoFeB rather than a continuous film.…”

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confidence: 45%

Effects of superparamagnetism in MgO based magnetic tunnel junctions

et al. 2009

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We have investigated the magnetic and transport behavior of MgO based magnetic tunnel junctions incorporating Co 40 Fe 40 B 20 free layers with thicknesses in the vicinity of 15 Å. The magnetic response of the free layer changes rapidly as its thickness decreases. Linear and hysteresis-free switching is obtained when the CoFeB free layer thickness is thinner than a critical thickness of ϳ15 Å. The tunneling magnetoresistance and hysteresis properties of the free layer change abruptly around the critical thickness. We have analyzed the transfer curves of junctions below the critical thickness and show that they agree well with the Langevin equation describing superparamagnetism. At even lower thicknesses, the total magnetic moment of the magnetic clusters decreases rapidly, possibly due to the reduction in the magnetic ordering temperature to below room temperature.

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confidence: 45%

Effects of superparamagnetism in MgO based magnetic tunnel junctions

et al. 2009

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“…Just as ferromagnetic cobalt ferrite has a much larger anisotropy than Co-Fe, the surface oxide here, Co-Fe-B-O x , is likely to be ferrimagnetic and of higher anisotropy than Co-Fe-B. Surface oxidation has previously been reported to increase anisotropy and reduce the switching field distribution for Co-Fe-B MTJs [41].…”

Section: Resultsmentioning

confidence: 91%

Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

et al. 2020

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Individual disk-shaped Co-Fe-B nanodots are driven into a superparamagnetic state by a spin-transfer torque, and their time-dependent magnetoresistance fluctuations are measured as a function of current. A thin layer of oxidation at the edges has a dramatic effect on the magnetization dynamics. A combination of experimental results and atomistic spin simulations shows that pinning to oxide grains can reduce the likelihood that fluctuations lead to reversal, and can even change the easy-axis direction. Exchange-bias loop shifts and training effects are observed even at room temperature after brief exposure to small fields. The results have implications for studies of core-shell nanoparticles and small magnetic tunnel junctions and spin-torque oscillators.

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“…periodic removal of mesh elements, random profiles, etc), different effects can be seen in the final device response. Additionally, an alternative strategy to improve the thermal stability of the nanostructures can resort to the edge oxidation of CoFeB and NiFe present at the free layer used to reduce the switching field distribution for memory applications [55]. The authors argued that the edge saturation magnetization decreases upon oxidation, suppressing the domain wall nucleation at edge defects, although an increase in the anisotropy field and slight decrease in TMR was observed [55].…”

Section: Fabricated Devicesmentioning

confidence: 99%

“…Additionally, an alternative strategy to improve the thermal stability of the nanostructures can resort to the edge oxidation of CoFeB and NiFe present at the free layer used to reduce the switching field distribution for memory applications [55]. The authors argued that the edge saturation magnetization decreases upon oxidation, suppressing the domain wall nucleation at edge defects, although an increase in the anisotropy field and slight decrease in TMR was observed [55]. This strategy could be extended to nanoscale sensors, helping to stabilize the ferromagnetic layers (sensing and pinned) behavior.…”

Section: Fabricated Devicesmentioning

confidence: 99%

Magnetoresistive nanosensors: controlling magnetism at the nanoscale

Leitao

Silva

Paz³

et al. 2015

Nanotechnology

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The ability to detect the magnetic fields that surround us has promoted vast technological advances in sensing techniques. Among those, magnetoresistive sensors display an unpaired spatial resolution. Here, we successfully control the linear range of nanometric sensors using an interfacial exchange bias sensing layer coupling. An effective matching of material properties and sensor geometry improves the nanosensor performance, with top sensitivities of 3.7% mT(-1). The experimental results are well supported by 3D micromagnetic and magneto-transport simulations.

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Suppression of Switching-Field Variation by Surface Oxidation Depending on the Shape of the CoFeB Free Layer

Cited by 5 publications

References 9 publications

Effects of superparamagnetism in MgO based magnetic tunnel junctions

Effects of superparamagnetism in MgO based magnetic tunnel junctions

Magnetoresistance Dynamics in Superparamagnetic Co−Fe−B Nanodots

Magnetoresistive nanosensors: controlling magnetism at the nanoscale

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