Hot Paper

"Spin-Orbit Torques..." in Phys. Rev. Lett.

3/12/2014

​"Spin-Orbit Torques in Co/Pd Multilayer Nanowires" Physical Review Letters (2013)

This work is a collaboration with Prof. H. Yang's group at the National University of Singapore
 
Current induced spin-orbit torques have been studied in ferromagnetic nanowires made of 20 nm thick Co/Pd multilayers with perpendicular magnetic anisotropy. Using Hall voltage and lock-in measurements, it is found that upon injection of an electric current both in-plane (Slonczewski-like) and perpendicular (fieldlike) torques build up in the nanowire. The torque efficiencies are found to be as large as 1.17 and 5 kOe at 108 A/cm2 for the in-plane and perpendicular components, respectively, which is surprisingly comparable to previous studies in ultrathin (1 nm) magnetic bilayers. We show that this result cannot be explained solely by spin Hall effect induced torque at the outer interfaces, indicating a probable contribution of the bulk of the Co/Pd multilayer.

This work has been published in
M. Jamali et al. Phys. Rev. Lett. 111, 246602 (2013).


Other hot papers

"Pauli Spin Blockade and the Ultrasmall Magnetic Field Effect" Physical Review Letters (2013)

This work is a collaboration with Dr. Danon from Niels Bohr Institute at the University of Copenhagen.

Based on the spin-blockade model for organic magnetoresistance, we present an analytic expression for the polaron-bipolaron transition rate, taking into account the effective nuclear fields on the two sites. We reveal the physics behind the qualitatively different magnetoconductance line shapes observed in experiment, as well as the ultrasmall magnetic field effect (USFE). Since our findings agree in detail with recent experiments, they also indirectly provide support for the spin-blockade interpretation of organic magnetoresistance. In addition, we predict the existence of a similar USFE in semiconductor double quantum dots tuned to the spin-blockade regime.

This work has been published in J. Danon, X. Wang and A. Manchon, Phys. Rev. Lett. 111, 066802 (2013).

"Diffusive Spin Dynamics in Ferromagnetic Thin Films with a Rashba Interaction" Physical Review Letters (2012)

In a ferromagnetic metal layer, the coupled charge and spin diffusion equations are obtained in the presence of both Rashba spin-orbit interaction and magnetism. The misalignment between the magnetization and the nonequilibrium spin density induced by the Rashba field gives rise to Rashba spin torque acting on the ferromagnetic order parameter. In a general form, we find that the Rashba torque consists of both in-plane and out-of-plane components. Numerical simulations on a two-dimensional nanowire consider the impact of diffusion on the Rashba torque and reveal a large enhancement to the ratio between in-plane and out-of-plane torques for thin wires. Our theory provides an explanation for the mechanism driving the magnetization switching in a single ferromagnet as observed in the recentexperiments.

This work has been published in X. Wang and A. Manchon, Phys. Rev. Lett. 108, 117201 (2012).


"Spin Relaxation in InGaN Quantum Disks in GaN Nanowires" Nano Letters (2012)

This work is a collaboration with Prof. Battacharya's group at the University of Michigan.

" The spin relaxation time of photoinduced conduction electrons has been measured in InGaN quantum disks in GaN nanowires as a function of temperature and In composition in the disks. The relaxation times are of the order of 100 ps at 300 K and are weakly dependent on temperature. Theoretical considerations show that the Elliott-Yafet scattering mechanism is essentially absent in these materials and the results are interpreted in terms of the DyakonovPerelrelaxation mechanism in the presence of Rashba spin-orbit coupling of the wurtzite structure. The calculated spin relaxation times are in good agreement with the measured values."

This investigation opens interesting directions in the search for semiconducting materials with long spin lifetime. This work has been published in Nano Letters: Animesh Banarjee, Fatih Dogan, Junseok Heo, Aurelien Manchon, Wei Guo, and Pallab Bhattacharya, Nano Letters 11, 5396 (2011).