Domain Wall Motion in Magnetic Helices

Rashba Torque Driven Domain Wall Motion in Magnetic Helices.

Oleksandr V. Pylypovskyi, Denis D. Sheka, Volodymyr P. Kravchuk, Kostiantyn V. Yershov, Denys Makarov & Yuri Gaididei

Scientific Reports 6, 23316 (2016)

(a) Schematics of magnetic helix with the easy-tangential anisotropy (magnetic moments are shown with red arrows, TNB-basis is shown with green arrows. (b) The rotation angle ψ for different torsions σ and curvatures ϰ. The onion state is energetically preferable in the grey region³⁷. Solid lines correspond to analytics³⁷, filled circles and open squares correspond to SLaSi and Nmag simulations, respectively; see Methods for details. (c,d) Discrete magnetic moments at equilibrium for right- and left-handed helices, respectively. The effective anisotropy axis is shown with thin black arrow e₁.

Domain wall motion driven by spin torque

Influence of uniaxial anisotropy on domain wall motion driven by spin torque.

P. Chureemart, R. F. L. Evans, I. D'Amico, and R. W. Chantrell

Phys. Rev. B 92, 054434 (2015)

(Top) The time variation of domain wall displacement with different current densities. (Bottom) The initial DW velocity as a function of current density: The critical current density, minimum current density required to move DW is 0.5MA/cm2.

Ultrafast switching of AF

Ultrafast switching of antiferromagnets via spin-transfer torque.
Ran Cheng, Matthew W. Daniels, Jian-Gang Zhu, and Di Xiao

Phys. Rev. B 91, 064423 (2015)

SW excitation by STT

Spin-Wave Excitation in Magnetic Insulators by Spin-Transfer TorqueJiang Xiao and Gerrit E. W. Bauer
Phys. Rev. Lett. 108, 217204 (2012)

An electrically insulating magnetic film of thickness d with magnetization m (∥ẑ at equilibrium) in contact with a normal metal. A spin current J_s∥ẑ is generated in the normal metal and absorbed by the ferromagnet.

Spin transfer torques in AF

Spin Pumping and Spin-Transfer Torques in Antiferromagnets.
Ran Cheng, Jiang Xiao, Qian Niu, and Arne Brataas
Phys. Rev. Lett. 113, 057601 (2014)

The two eigenmodes of Eq. (2) have opposite chiralities and opposite ratios between the cone angles of m1 and m2. A magnetic field along the easy axis breaks the degeneracy of the two modes.

Interactions of SWs and DWs in a nanowire

Interaction between propagating spin waves and domain walls on a ferromagnetic nanowire.
J.-S. Kim, M. Stärk, and M. Kläui, J. Yoon and C.-Y. You, L. Lopez-Diaz and E. Martinez
Phys. Rev. B 85, 174428 (2012)

(a) The SW amplitudes as a function of time (t = 5.0–5.5 ns with fH = 6.0 GHz, B0 = 200 mT, and Bext = 0.5 mT) at the TW position (x = 500 nm and x = 700 nm) (black line, the SW amplitude without a TW; red line, the SW amplitude with a TW). (b) The FFT spectra of the SW amplitude for the case of (a) at the TW position (x = 500 nm). (c) The SW amplitudes as a function of time at x = 500 nm (t = 5.0–10.0 ns with fH = 11.0 GHz, B0 = 200 mT, and Bext = 0.8 mT). (d) The FFT spectrum of the SW amplitude for the case of  (c) at the TW position. Inset shows the snapshots of the y-component magnetization for two different simulation times.

Spin torque

Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum.
Luqiao Liu, Chi-Feng Pai, Y. Li, H. W. Tseng, D. C. Ralph, R. A. Buhrman
Science 336, 555 (2012)

ST-FMR induced by the spin Hall effect at room temperature. (A) Sample geometry for the ST-FMR measurement. IRF and HRF represent the applied radio frequency current and the corresponding Oersted field. Tau_h is the torque on the magnetization due to the Oersted field, and Tau_ST is the spin-transfer torque from the spin Hall effect. Resonant line shapes of the STFMR signals under a driving frequency f = 9 GHz for (B) CoFeB(4 nm)/Ta(8 nm) and (C) CoFeB(3 nm)/Pt
(6 nm). The squares represent experimental data, whereas the red curves are fits to a sum of symmetric and antisymmetric Lorentzians. From the ratio of the symmetric and antisymmeteric peak components in (C), we determine the JS/Je ratio for Pt to be ~0.07, consistent with earlier work (19). Vmix is the measured dc voltage due to the mixing of oscillating resistance and radio frequency current. The inset to (B) shows the dependence of the frequency f on the resonance magnetic field, in agreement with the Kittel formula (solid curve). (D) The resonance linewidth as determined from ST-FMR signals such as
those shown in (B) and (C) at different resonance frequencies. The Gilbert damping coefficients a for Ta and Pt are calculated from the linear fits to these linewidth data. CFB, CoFeB.

Optical spin transfer torque observed

Experimental observation of the optical spin transfer torque.
P. Nemec1, E. Rozkotová, N. Tesarová, F. Trojánek, E. De Ranieri, K. Olejník, J. Zemen, V. Novák, M. Cukr, P. Malý and T. Jungwirth
Nature Physics AOL (2012)

Schematic illustration of the optical spin transfer torque. a, Schematic illustration of the optical spin transfer torque in the large spin lifetime limit. The rate P of the photo-carrier spin injection along the light propagation axis ˆn (normal to the sample plane) is completely transferred to the optical spin transfer torque (OSTT) acting along the normal to the sample plane on the magnetization M of the ferromagnet. The steady-state component of the injected spin density s0 is oriented in the plane of the sample and perpendicular to the in-plane equilibrium magnetization vector. The fast precessing component of the spin of a photo-carrier (small upper arrows) relaxes to the environment at a random orientation, producing a zero net momentum transfer to the environment. This picture applies to photo-electrons in (Ga, Mn)As. b, A weak torque acting on M (red arrow) produced by photo-carriers with a short spin lifetime. Most of the spin angular moment is transferred to the environment in this limit. For photo-holes in (Ga, Mn)As this picture is more relevant than the picture of the strong optical spin transfer torque shown in a.

Nanooscillator characterized by MRFM

Quantitative MRFM characterization of the autonomous and forced dynamics in a spin transfer nano-oscillator.
A. Hamadeh, G. de Loubens, V.V. Naletov, J. Grollier, C. Ulysse, V. Cros, and O. Klein
ArXiv 1201.6344 (2012)

Phase diagram of the STNO autonomous dynamics measured by MRFM.

Spin transfer in thick DW

Spin-transfer torque in a thick Néel domain wall
P. Balaz, V. K. Dugaev, and J. Barnás
Phys. Rev. B 85, 024416 (2012)

(a) The nonadiabaticity parameter β and (b) the nonadiabaticity parameter γ as a function of the exchange
parameter J , calculated for indicated values of η.

First-principles calculation of the nonadiabatic spin transfer torque in Ni and Fe.
Keith Gilmore, Ion Garate, Allan H. MacDonald, and M. D. Stiles
Phys. Rev. B 84, 224412 (2011)

Spin-transfer torque parameter versus resistivity for several ratios (r = 0.5, 1.0, 2.0) of spin-dependent scattering rates for Ni. The top panel gives β, the middle panel β/α, and the bottom panel βσP/(ασ). The dashed vertical lines indicate
the approximate room-temperature resistivity.

Perpendicular spin torque in MTJs

Measurement of perpendicular spin torque at high bias via the pulsed switching phase diagram
Seung-Young Park, Younghun Jo, and Kyung-Jin Lee
Phys. Rev. B 84, 214417 (2011)

Experimental measurements of (a) dc switching phase diagram and (b) pulsed switching phase diagrams. In
(b), the switching boundaries of dc switching phase diagram is added for comparison (red dashed lines).

Spin-transfer-torque-induced phenomena

Special Section in J. Phys.D containing, among others, the following review articles:


1) A brief review of field- and current-driven domain-wall motion.
Junya Shibata, Gen Tatara and Hiroshi Kohno
JPD 44, 384004 (2011)

Schematic of the translation motion of the domain wall in a uniform magnetic field.

2) Current-induced domain wall motion in nanoscale ferromagnetic element. G Malinowski, O Boulle and M Kläui
JPD 44, 384005 (2011)

Schematic of a magnetic wire with domains. The colour and the arrows indicate the magnetization direction.

Radio-frequency current on spin-torque

Effects of radio-frequency current on critical fields for magnetization reversal in spin-torque devices.
W. Chen, S. H. Florez, J. A. Katine, M. J. Carey, L. Folks, and B. D. Terris
Phys. Rev. B 84, 054459 (2011)

(a), (b) Contour plots of dV/dI as a function of both the dc bias and the applied magnetic field, with the field-sweep directions from the AP to P state and from the P to AP state, respectively. (c) Schematic of the switching
boundaries, with the area of interest divided into several typical regimes.

Spin torque induced by Rashba effect

Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer.
Ioan Mihai Miron, Gilles Gaudin, Stéphane Auffret, Bernard Rodmacq, Alain Schuhl, Stefania Pizzini, Jan Vogel and Pietro Gambardella
Nature Mater. 9, 230 (2010)

Differential Kerr microscopy images recorded after current pulse injection.