Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Li, Minghua; Lü, Jitao; Yu, Guoqiang; Li, Xiang; Han, Gang; Chen, Xi; Shi, Hui; Yu, Guanghua; Amiri, Pedram Khalili; Wang, Kang L.

doi:10.1063/1.4947075

Cited by 9 publications

(8 citation statements)

References 31 publications

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“…Surprisingly, by depositing the Mo layer with an oblique angle, fieldfree current-induced magnetization switching can be realized. This discovery implies that strong spin- 13 orbit interaction materials or spin Hall sources are not always necessary in achieving field-free current-induced switching, and "to wedge or not to wedge" during the thin film deposition process is a more critical factor.…”

Section: Discussionmentioning

confidence: 99%

“…Besides Ta, several other HM materials have also been demonstrated to be suitable buffer layers for enhancing the PMA in HM/CoFeB/MgO structures. For 3 instance, thermally annealed Hf/CoFeB/MgO [11] and Mo/CoFeB/MgO [12,13] have both been shown to gain greater PMA energy densities while compare to that of Ta/CoFeB/MgO. Surprisingly, Mo/CoFeB/MgO heterostructure can survive thermal annealing up to 450˚C, which makes it an attractive candidate for replacing Ta as the standard p-MTJ buffer layer structure that can be compatible with modern CMOS processing [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo -Based Magnetic Heterostructures

et al. 2018

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Magnetic heterostructure Mo/CoFeB/MgO has strong perpendicular magnetic anisotropy and thermal stability. Through current-induced hysteresis loop shift measurements, we show that the dampinglike spin-orbit torque (SOT) efficiency of Mo/CoFeB/MgO heterostructures is 0.003 0.001 DL     and fairly independent of the annealing temperature from 300˚C to 400˚C. Though DL  is small while compare to those from Ta or Wbased heterostructures, reversible current-induced SOT switching of a thermally-stable Mo/CoFeB/MgO heterostruture can still be achieved. Furthermore, we observe field-free current-induced switching from a Mo/CoFeB/MgO structure with the Mo layer being wedge-deposited. Our results indicate that even for a weak spin-orbit interaction 4d transition metal such as Mo, it is still possible to generate sufficient spin current for conventional SOT switching and to realize field-free current-induced switching by structural engineering. 

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo -Based Magnetic Heterostructures

et al. 2018

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“…When the annealing temperature is greater than 350 °C, the K eff of Ta/Mo and Ta/Hf buffer samples decrease with increasing temperature, which suggests significant Ta diffusion into the CoFeB and even MgO layers . We also observe that the CoFeB/MgO interface widths increase at temperatures above 350 °C (Figure B).…”

Section: Resultsmentioning

confidence: 66%

“…After annealing at 200 °C, the Ta buffer sample exhibits a decrease in Ms, likely due to Ta diffusion, whereas the Ms of Ta/Hf and Ta/Mo increase due to the Hf or Mo layer acting as a Ta diffusion sink . As annealing temperature increases, K eff increases rapidly for Ta/Mo and gradually for Ta/Hf, and both reach a maximum at 350 °C.…”

Section: Resultsmentioning

confidence: 99%

Characterization of the interfacial structure and perpendicular magnetic anisotropy in CoFeB‐MgO structures with different buffer layers

Shi

Fang

et al. 2017

Surface & Interface Analysis

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In this study, we describe the deposition of Hf and Mo metal layers individually on Ta to compose new buffer layers, ie, Ta/Hf and Ta/Mo, where CoFeB/MgO stacks are deposited using magnetron sputtering. The synthesised Ta/Hf buffer has higher surface roughness, while the Ta/Mo buffer has lower surface roughness as compared with the Ta buffer. The surface roughness of the buffer appears to influence the interface of the subsequently deposited layers, resulting in rougher or smoother CoFeB/MgO interfaces. Additionally, we present a report on the magnetic properties of Ta, Ta/Hf, and Ta/Mo buffer samples. As the annealing temperature is below 200°C, the saturation magnetisation (Ms) values for all buffer layers increase at similar rates, whereas the effective magnetic anisotropy energy (K eff ) values increase at varying rates. After annealing at 350°C, K eff reaches its maximum value for Ta/Hf and Ta/Mo buffer layers, whereas the CoFeB/MgO interface width decreases to a minimum value. The width increases as the annealing temperature is increased over 350°C, and K eff gradually decreases with increase in the annealing temperature. The CoFeB/MgO interface width is primarily dependent on the buffer/CoFeB interface width, which is a critical parameter to obtain high perpendicular magnetic anisotropy (PMA) and high-quality films. This work provides perspectives for understanding and controlling PMA from the viewpoint of interfacial structure. Subsequent studies found that the observed PMA in Ta/CoFeB/MgO sandwiches originates primarily from the CoFeB/MgO interface. 1,[4][5][6][7] More recently, the CoFeB/nonmagnetic metal counter interface has been reported to also affect the perpendicular anisotropy originating from CoFeB/MgO. [7][8][9][10][11][12] Typically, the thickness of CoFeB must be less than 1.5 nm in order to obtain a perpendicular easy axis. 1,8,12 Owing to the limitations on the required thickness, any influence of the counter interfaces of CoFeB with the buffer layer and MgO on the structural, morphological, and PMA properties of CoFeB layers warrants careful investigation.In the X-ray reflectivity (XRR) measurement conducted herein, we use Cu as the anode material and an X-ray wavelength of 0.154 nm to investigate the interface till submonolayer resolution in terms of roughness and/or intermixing. 13 XRR and atomic force microscopy (AFM) measurements were used to analyse changes in the interface structure during annealing.

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“…The annealing process is responsible for the strong PMA, which causes the rearrangement of elements at their interfaces, resulting in elimination of disorder generated during sputtering growth . In general, the PMA property, i.e., switching of the magnetic easy axis from parallel to perpendicular plane direction was observed for Heusler alloy films at RT and/or after annealing, which could be attributed to the improved quality of MgO layer with optimized oxygen content .…”

Section: Resultsmentioning

confidence: 99%

Robust Perpendicular Magnetic Anisotropy in MgO/Co₂FeAl/MgO Stacks Induced by MgO over Layer and Annealing Temperature

Saravanan

Muthuvel

Delhibabu

et al. 2018

Physica Status Solidi (a)

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Perpendicular magnetic anisotropy (PMA) in Co2FeAl (CFA)/MgO stacks deposited on the MgO buffer layer is studied as a function of MgO over‐layer thickness and annealing temperature. It reveals that MgO over‐layer (thickness between 0 and 1.5 nm) improves the PMA of CFA grown on MgO buffer layer. It is identified that MgO over‐layer thickness is a crucial factor that affects the magnetic anisotropy. The maximum effective PMA energy density (Keff) of ≈1.22 × 106 erg cm−3 is observed at 400 °C. Besides, PMA is also realized for room temperature (RT) films. Moreover, enhancement in the perpendicular saturation magnetization (Ms┴) with PMA is effectively induced by the CFA/MgO or CFA/Mo interface and is discussed in detail. The grain distribution and surface roughness are investigated by atomic force microscopy (AFM) for without and with MgO over‐layer in MgO/CFA/tMgO (0 and 0.5 nm)/Mo stacks at higher annealing temperature. Therefore, this MgO/CFA/MgO can be an ideal system for the p‐MTJs‐based new generation low power consuming large density data storage spintronic devices with improved thermal stability.

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Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Cited by 9 publications

References 31 publications

Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo -Based Magnetic Heterostructures

Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo -Based Magnetic Heterostructures

Characterization of the interfacial structure and perpendicular magnetic anisotropy in CoFeB‐MgO structures with different buffer layers

Robust Perpendicular Magnetic Anisotropy in MgO/Co₂FeAl/MgO Stacks Induced by MgO over Layer and Annealing Temperature

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Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co20Fe60B20/MgO/Ta films

Cited by 9 publications

References 31 publications

Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo -Based Magnetic Heterostructures

Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo -Based Magnetic Heterostructures

Characterization of the interfacial structure and perpendicular magnetic anisotropy in CoFeB‐MgO structures with different buffer layers

Robust Perpendicular Magnetic Anisotropy in MgO/Co2FeAl/MgO Stacks Induced by MgO over Layer and Annealing Temperature

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Robust Perpendicular Magnetic Anisotropy in MgO/Co₂FeAl/MgO Stacks Induced by MgO over Layer and Annealing Temperature