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Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents.

Sharma S, Muralidharan B, Tulapurkar A - Sci Rep (2015)

Bottom Line: We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000.A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples.Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.

ABSTRACT
We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

No MeSH data available.


Working principle and device design.(a) Schematic depicting the principal idea of the proposal which comprises a domain wall magnet with the incident non-uniform spin current and a uniform magnetic field. The domain wall is shown at an arbitrary instantaneous position. The non-uniform spin current is incident on a region spanning one-half of the magnet. (b) A 3D schematic of the proposed device design. A strip of Tantalum localized in the desired region of the domain wall magnet, connected to a current source generates the desired spin current. The applied magnetic field along the −z axis is not shown here for clarity. (c) A circuit diagram representing the device schematic in (b). r1 is the resistance of the part of Tantalum strip between the constant current source, ‘I’, and MTJ, and similarly r2. (d) Zoomed-in motion of middle spin marked in (a), depicting the rotation it undergoes which gets converted into motion via its hard axis anisotropy. The orange colored region is the portion where spin current is non-zero.
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f1: Working principle and device design.(a) Schematic depicting the principal idea of the proposal which comprises a domain wall magnet with the incident non-uniform spin current and a uniform magnetic field. The domain wall is shown at an arbitrary instantaneous position. The non-uniform spin current is incident on a region spanning one-half of the magnet. (b) A 3D schematic of the proposed device design. A strip of Tantalum localized in the desired region of the domain wall magnet, connected to a current source generates the desired spin current. The applied magnetic field along the −z axis is not shown here for clarity. (c) A circuit diagram representing the device schematic in (b). r1 is the resistance of the part of Tantalum strip between the constant current source, ‘I’, and MTJ, and similarly r2. (d) Zoomed-in motion of middle spin marked in (a), depicting the rotation it undergoes which gets converted into motion via its hard axis anisotropy. The orange colored region is the portion where spin current is non-zero.

Mentions: The interest in dynamics of magnetic domain walls has been active for decades789101112, recently intensified by the discovery of current-driven domain wall motion131415 and its related applications in nanoelectronics5161718. Field driven oscillations have also been observed and studied1119 for a long time. However, these oscillations are accompanied by a drift which makes them unusable as a device. On a different note, vertical injection of uniform spin current is proposed as a means for high domain wall velocities202122. Here, we propose stable oscillations caused by a constant magnetic field whose drift is canceled by a vertically injected non-uniform spin current as depicted in the schematic in Fig. 1(a), thereby resulting in a stable periodic motion.


Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents.

Sharma S, Muralidharan B, Tulapurkar A - Sci Rep (2015)

Working principle and device design.(a) Schematic depicting the principal idea of the proposal which comprises a domain wall magnet with the incident non-uniform spin current and a uniform magnetic field. The domain wall is shown at an arbitrary instantaneous position. The non-uniform spin current is incident on a region spanning one-half of the magnet. (b) A 3D schematic of the proposed device design. A strip of Tantalum localized in the desired region of the domain wall magnet, connected to a current source generates the desired spin current. The applied magnetic field along the −z axis is not shown here for clarity. (c) A circuit diagram representing the device schematic in (b). r1 is the resistance of the part of Tantalum strip between the constant current source, ‘I’, and MTJ, and similarly r2. (d) Zoomed-in motion of middle spin marked in (a), depicting the rotation it undergoes which gets converted into motion via its hard axis anisotropy. The orange colored region is the portion where spin current is non-zero.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588506&req=5

f1: Working principle and device design.(a) Schematic depicting the principal idea of the proposal which comprises a domain wall magnet with the incident non-uniform spin current and a uniform magnetic field. The domain wall is shown at an arbitrary instantaneous position. The non-uniform spin current is incident on a region spanning one-half of the magnet. (b) A 3D schematic of the proposed device design. A strip of Tantalum localized in the desired region of the domain wall magnet, connected to a current source generates the desired spin current. The applied magnetic field along the −z axis is not shown here for clarity. (c) A circuit diagram representing the device schematic in (b). r1 is the resistance of the part of Tantalum strip between the constant current source, ‘I’, and MTJ, and similarly r2. (d) Zoomed-in motion of middle spin marked in (a), depicting the rotation it undergoes which gets converted into motion via its hard axis anisotropy. The orange colored region is the portion where spin current is non-zero.
Mentions: The interest in dynamics of magnetic domain walls has been active for decades789101112, recently intensified by the discovery of current-driven domain wall motion131415 and its related applications in nanoelectronics5161718. Field driven oscillations have also been observed and studied1119 for a long time. However, these oscillations are accompanied by a drift which makes them unusable as a device. On a different note, vertical injection of uniform spin current is proposed as a means for high domain wall velocities202122. Here, we propose stable oscillations caused by a constant magnetic field whose drift is canceled by a vertically injected non-uniform spin current as depicted in the schematic in Fig. 1(a), thereby resulting in a stable periodic motion.

Bottom Line: We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000.A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples.Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.

ABSTRACT
We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

No MeSH data available.