Current induced vortices in multi-nanocontact spin-torque devices

Sani, Sohrab R.; Persson, Johan; Mohseni, Seyed Majid; Fallahi, Vahid; Åkerman, Johan

doi:10.1063/1.3556960

Cited by 23 publications

(18 citation statements)

References 20 publications

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“…The DC drive current is injected perpendicularly into the films by means of a 100 nm diameter, electron-beam lithography defined circular opening in the insulating SiO 2 , filled with Cu. Details of the fabrication process can be found in [13]. The nano-contact is connected to the signal line of an on-chip ground-signal-ground (GSG) coplanar waveguide, with its ground lines connected to the bottom of the film stack.…”

Section: Measurementmentioning

confidence: 99%

Triple mode-jumping in a spin torque oscillator

Eklund

Sani

Mohseni

et al. 2013

2013 22nd International Conference on Noise and Fluctuations (ICNF)

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Abstract-In a nano-contact Co/Cu/NiFe spin torque oscillator, mode-jumping between up to three frequencies within 22.5-24.0 GHz is electrically observed in the time domain. The measurements reveal toggling between two states with differing oscillation amplitude, of which the low-amplitude state is further divided into two rapidly alternating modes. Analysis of the mode dwell time statistics and the total time spent in each mode is carried out, and it is found that in both aspects the balance between the modes is greatly altered with the DC drive current.

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Section: Measurementmentioning

confidence: 99%

Triple mode-jumping in a spin torque oscillator

Eklund

Sani

Mohseni

et al. 2013

2013 22nd International Conference on Noise and Fluctuations (ICNF)

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“…On the one hand, by using Co/Ni multilayers exhibiting perpendicular magnetic anisotropy, NC-STOs have been shown to support steady magnetization dynamics at low external fields [6] and even the excitation of localized modes known as magnetic dissipative droplets [7][8][9][10]. On the other hand, using soft magnets such as NiFe, the existence of propagating [11,12], localized [12][13][14][15], and vortex [16,17] modes has been demonstrated, depending on both the strength and the direction of the external magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Propagating spin waves excited by spin-transfer torque: A combined electrical and optical study

et al. 2015

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Nanocontact spin-torque oscillators are devices in which the generation of propagating spin waves can be sustained by spin transfer torque. In the present paper, we perform combined electrical and optical measurements in a single experimental setup to systematically investigate the excitation of spin waves by a nanocontact spin-torque oscillator and their propagation in a Ni 80 Fe 20 extended layer. By using microfocused Brillouin light scattering we observe an anisotropic emission of spin waves, due to the broken symmetry imposed by the inhomogeneous Oersted field generated by the injected current. In particular, spin waves propagate on the side of the nanocontact where the Oersted field and the in-plane component of the applied magnetic field are antiparallel, while propagation is inhibited on the opposite side. Moreover, propagating spin waves are efficiently excited only in a limited frequency range corresponding to wavevectors inversely proportional to the size of the nanocontact. This frequency range obeys the dispersion relation for exchange-dominated spin waves in the far field, as confirmed by micromagnetic simulations of similar devices. The present results have direct consequences for spin wave based applications, such as synchronization, computation, and magnonics.

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“…For example, in easyplane material based devices such as STNOs with Permalloy free layers, in addition to vortices [26][27][28], both propa-gating spin waves [29][30][31][32][33][34][35][36] and self-localized spin wave bullet solitons [31][32][33]37] can be generated experimentally.…”

Section: Introductionmentioning

confidence: 99%

Magnetic droplet solitons in orthogonal spin valves

Chung

Mohseni

Eklund

et al. 2015

Low Temperature Physics

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We review the recent experimental advancements in the realization and understanding of magnetic droplet solitons generated by spin transfer torque in orthogonal nanocontact based spin torque nanooscillators (STNOs) fabricated on extended spin valves and spin valve nanowires. The magnetic droplets are detected and studied using the STNO microwave signal and its resistance, the latter both quasistatically and time-resolved. The droplet nucleation current is found to have a minimum at intermediate magnetic field strengths and the nature of the nucleation changes gradually from a single sharp step well above this field, mode-hopping around the minimum, and continuous at low fields. The mode-hopping and continuous transitions are ascribed to droplet drift instability and re-nucleation at different time scales, which is corroborated by time-resolved measurements. We argue that the use of tilted anisotropy fixed layers could reduce the nucleation current further, move the nucleation current minimum to lower fields, and potentially remove the need for an applied magnetic field altogether. Finally, evidence of an edge mode droplet in a nanowire is presented. PACS: 75.30.Ds Spin waves;75.75.-c Magnetic properties of nanostructures.

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Current induced vortices in multi-nanocontact spin-torque devices

Cited by 23 publications

References 20 publications

Triple mode-jumping in a spin torque oscillator

Triple mode-jumping in a spin torque oscillator

Propagating spin waves excited by spin-transfer torque: A combined electrical and optical study

Magnetic droplet solitons in orthogonal spin valves

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