Spin-transfer-torque-induced zero-field microwave oscillator using a magnetic easy cone state

Jang, Peong Hwa; Lee, Seo Won; Lee, Kyung Jin

doi:10.1016/j.cap.2016.09.004

Cited by 10 publications

(6 citation statements)

References 32 publications

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“…This restriction is intrinsically valid for weak K 2 case for any value of the H x . In contrast, it fails for very small H x (<1 mT, planar saturation field ∼300 mT) and small voltages in the case for the strong K 2 since there is no any static equilibrium in such condition as previously reported by Jang et al [43] for H x = 0. Using (7) and (8) we can express this condition in the limit H x → 0:…”

Section: Analytical Solution For In-plane Field Configurationsupporting

confidence: 60%

“…One might note that the above case a) corresponds to the situation of the existence of an easy-cone state as recently reported in Ref. [43] while the case b) is the common perpendicular state ("up" or "down"). The relations given by Eqs.…”

Section: Analytical Solution For In-plane Field Configurationmentioning

confidence: 61%

“…In the case of strong K 2 and in the limit of very small applied field, one might notice that the analytical lines become shorter and the numerical values are not following anymore the analytical prediction. This discrepancy is due to the fact that before the switching in a very symmetric geometry, the magnetization oscillates on the easy-cone as predicted by [43]. This is an illustration of the difference between V cr and switching voltage V sw mentioned earlier and pointed out in FIG.…”

Section: Energetic Efficiency Of the Magnetization Switchingmentioning

confidence: 64%

“…[26]) if K 2 = 0 and for this case the critical voltage coincides with the switching voltage at zero field V sw,0 . In the easy-cone regime, V cr,0 equals to zero since once the voltage is applied the magnetization precesses around the easy-cone [43]. For this very symmetric configuration it is possible to estimate the switching voltage using the approach from Ref.…”

Section: Energetic Efficiency Of the Magnetization Switchingmentioning

confidence: 99%

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Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

et al. 2017

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International audienceExperimental measurements performed on MgO-based perpendicular magnetic tunnel junctions show a strong dependence of the stability voltage-field diagrams as a function of the direction of the magnetic field with respect to the plane of the sample. When the magnetic field is applied in-plane, systematic nonlinear phase boundaries are observed for various lateral sizes. The simulation results based on the phenomenological Landau-Lifshitz-Gilbert equation including the in-plane and out-of-plane spin transfer torques are consistent with the measurements if a second-order anisotropy contribution is considered. Furthermore, performing the stability analysis in linear approximation allowed us to analytically extract the critical switching voltage at zero temperature in the presence of an in-plane field. This study indicates that in the noncollinear geometry investigations are suitable to detect the presence of the second-order term in the anisotropy. Such higher order anisotropy term can yield an easy-cone anisotropy which reduces the thermal stability factor but allows for more reproducible spin transfer torque switching due to a reduced stochasticity of the switching. As a result, the energy per write event decreases much faster than the thermal stability factor as the second-order anisotropy becomes more negative. Easy-cone anisotropy can be useful for fast-switching spin transfer torque magnetic random access memories provided the thermal stability can be maintained above the required value for a given memory specification

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Section: Analytical Solution For In-plane Field Configurationsupporting

confidence: 60%

Section: Analytical Solution For In-plane Field Configurationmentioning

confidence: 61%

Section: Energetic Efficiency Of the Magnetization Switchingmentioning

confidence: 64%

Section: Energetic Efficiency Of the Magnetization Switchingmentioning

confidence: 99%

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Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

et al. 2017

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“…Subsequently, several experimental studies focused on either this structure, putting in evidence the second order magnetic anisotropy for pMTJs with thin CoFeB layers (1.2-1.35 nm) using FMR, or magnetoresistance for patterned structures. [12][13][14] Other studies explored the influence of this effect on pMTJ state diagrams. [15][16][17][18][19] Reference 19 considered the influence of a second order anisotropy on the switching current.…”

mentioning

confidence: 99%

Increased energy efficiency spin-torque switching of magnetic tunnel junction devices with a higher order perpendicular magnetic anisotropy

Lavanant

Petit-Watelot

Kent

et al. 2019

Applied Physics Letters

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Intrinsic origin of interfacial second-order magnetic anisotropy in ferromagnet/normal metal heterostructures

et al. 2020

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Interfacial perpendicular magnetic anisotropy, which is characterized by the firstorder (K1) and second-order (K2) anisotropies, is the core phenomenon for nonvolatile magnetic devices. A sizable K2 satisfying a specific condition stabilizes the easy-cone state, where equilibrium magnetization forms at an angle from the film normal. The easy-cone state offers intriguing possibilities for advanced spintronic devices and unique spin textures, such as spin superfluids and easy-cone domain walls. Experimental realization of the easy-cone state requires understanding the origin of K2, thereby enhancing K2. However, previously proposed origins of K2 cannot fully account for experimental results. Here we show experimentally that K2 scales almost linearly with the work-function difference between the Co and X layers in Pt/Co/X heterostructures (X = Pd, Cu, Pt, Mo, Ru, W, and Ta), suggesting the central role of the inversion asymmetry in K2. Our result provides a guideline for enhancing K2 and realizing magnetic applications based on the easy-cone state.

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Spin-transfer-torque-induced zero-field microwave oscillator using a magnetic easy cone state

Cited by 10 publications

References 32 publications

Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

Increased energy efficiency spin-torque switching of magnetic tunnel junction devices with a higher order perpendicular magnetic anisotropy

Intrinsic origin of interfacial second-order magnetic anisotropy in ferromagnet/normal metal heterostructures

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