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Study of Spin Orbit Torque and Application of Spin Hall Magnetoresistance Sensor.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Study of Spin Orbit Torque and Application of Spin Hall Magnetoresistance Sensor./
作者:	Ling, Lu.
面頁冊數:	1 online resource (171 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
Contained By:	Dissertations Abstracts International84-04B.
標題:	Integrated circuits. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29353132click for full text (PQDT)
ISBN:	9798352687420

Study of Spin Orbit Torque and Application of Spin Hall Magnetoresistance Sensor.
Ling, Lu.

Study of Spin Orbit Torque and Application of Spin Hall Magnetoresistance Sensor. - 1 online resource (171 pages)

Source: Dissertations Abstracts International, Volume: 84-04, Section: B.

Thesis (Ph.D.)--National University of Singapore (Singapore), 2022.

Includes bibliographical references

Extensive efforts have been devoted to studies of spin-orbit torque (SOT) in magnetic heterostructures in recent years, in particular in ferromagnet/heavy metal bilayers. On one hand, various mechanisms leading to the SOT have been investigated along with various methods to quantify the SOT effective fields. On the other hand, there are growing interests to exploit the SOT for device applications particularly in magnetic random-access memory (MRAM). Although the bilayer has proven to be an effective SOT generator, single-layer ferromagnets that can generate local non-equilibrium spins electrically would be more appealing for practical applications as they do not suffer from thickness limitation and can potentially be more advantageous in terms of power consumption. Of our particular interest are ferromagnets which exhibit large anomalous Hall effect (AHE) as the combination of AHE and spin rotation at the surface has been shown to be able to generate SOT. On the application front, our group has recently developed a spin Hall magnetoresistances (SMR) sensor which exhibits high-sensitivity, zero offset and negligible hysteresis, and therefore, it would be of interest to explore practical applications which can fully make use of these unique characteristics. In this context, in the first part of this thesis, we investigate quantitatively the influence of Pt composition on SOT in single-layer FeMnPt films with or without composition gradient. Damping-like (DL) and field-like (FL) torques are evaluated by both nonlinear magnetoresistance and harmonic Hall measurements. In films with uniform composition, the DL torque significantly increases with the addition of Pt, while the FL torque slightly decreases. The SOT decreases with increasing thickness, suggesting a surface origin of the observed SOT. A model based on AHE and surface spin scattering is introduced to account for the experimental observations. On the other hand, the introduction of composition gradient does not lead to observable changes in the SOT, which deserves further investigations.In the second part of this thesis, we demonstrate applications of the SMR sensor in eddy current testing (ECT) and stray field mapping. The ECT and stray field detection are two useful non-destructive techniques in various industries to check the quality of conductive and ferromagnetic materials. Presence of defects, stress or composition inhomogeneity can be revealed by monitoring the change in magnetic field, which comes from eddy currents in ECT or the material itself if it is magnetic. One major limitation in these two techniques is the complicated test setup and signal processing algorithms that are required to extract the defect information. The AC-driven capability, high sensitivity and low noise make the SMR sensor uniquely suited for such applications. The defect information can be directly extracted from the output of the sensor, and no additional demodulator nor lock-in amplifier is needed to detect and process the signals. For ECT applications, since both the excitation coil and sensor itself are excited by AC current, we investigate how the excitation waveform and frequency combinations affect the detectivity of the system. It is found that square wave current with the same frequency applied to both the coil and the sensor gives the largest crack signal and a small baseline shift.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798352687420Subjects--Topical Terms:

584067
Integrated circuits.
Index Terms--Genre/Form:

542853
Electronic books.

Study of Spin Orbit Torque and Application of Spin Hall Magnetoresistance Sensor.
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245 1 0 $a Study of Spin Orbit Torque and Application of Spin Hall Magnetoresistance Sensor.
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500 $a Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
500 $a Advisor: Yihong, Wu; Younan, Hua.
502 $a Thesis (Ph.D.)--National University of Singapore (Singapore), 2022.
504 $a Includes bibliographical references
520 $a Extensive efforts have been devoted to studies of spin-orbit torque (SOT) in magnetic heterostructures in recent years, in particular in ferromagnet/heavy metal bilayers. On one hand, various mechanisms leading to the SOT have been investigated along with various methods to quantify the SOT effective fields. On the other hand, there are growing interests to exploit the SOT for device applications particularly in magnetic random-access memory (MRAM). Although the bilayer has proven to be an effective SOT generator, single-layer ferromagnets that can generate local non-equilibrium spins electrically would be more appealing for practical applications as they do not suffer from thickness limitation and can potentially be more advantageous in terms of power consumption. Of our particular interest are ferromagnets which exhibit large anomalous Hall effect (AHE) as the combination of AHE and spin rotation at the surface has been shown to be able to generate SOT. On the application front, our group has recently developed a spin Hall magnetoresistances (SMR) sensor which exhibits high-sensitivity, zero offset and negligible hysteresis, and therefore, it would be of interest to explore practical applications which can fully make use of these unique characteristics. In this context, in the first part of this thesis, we investigate quantitatively the influence of Pt composition on SOT in single-layer FeMnPt films with or without composition gradient. Damping-like (DL) and field-like (FL) torques are evaluated by both nonlinear magnetoresistance and harmonic Hall measurements. In films with uniform composition, the DL torque significantly increases with the addition of Pt, while the FL torque slightly decreases. The SOT decreases with increasing thickness, suggesting a surface origin of the observed SOT. A model based on AHE and surface spin scattering is introduced to account for the experimental observations. On the other hand, the introduction of composition gradient does not lead to observable changes in the SOT, which deserves further investigations.In the second part of this thesis, we demonstrate applications of the SMR sensor in eddy current testing (ECT) and stray field mapping. The ECT and stray field detection are two useful non-destructive techniques in various industries to check the quality of conductive and ferromagnetic materials. Presence of defects, stress or composition inhomogeneity can be revealed by monitoring the change in magnetic field, which comes from eddy currents in ECT or the material itself if it is magnetic. One major limitation in these two techniques is the complicated test setup and signal processing algorithms that are required to extract the defect information. The AC-driven capability, high sensitivity and low noise make the SMR sensor uniquely suited for such applications. The defect information can be directly extracted from the output of the sensor, and no additional demodulator nor lock-in amplifier is needed to detect and process the signals. For ECT applications, since both the excitation coil and sensor itself are excited by AC current, we investigate how the excitation waveform and frequency combinations affect the detectivity of the system. It is found that square wave current with the same frequency applied to both the coil and the sensor gives the largest crack signal and a small baseline shift.
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538 $a Mode of access: World Wide Web
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650 4 $a Cracks. $3 3686873
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