Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current-induced switching

Baldrati, L.*; Schmitt, C.*; Gomonay, O.*; Lebrun, R.*; Ramos, R.*; Saito, Eiji; Sinova, J.*; Klui, M.*

Physical Review Letters, 125(7), p.077201_1 - 077201_6, 2020/08

https://doi.org/10.1103/PhysRevLett.125.077201

Spin caloric effects in antiferromagnets assisted by an external spin current

Gomonay, O.*; Yamamoto, Kei; Sinova, J.*

Journal of Physics D; Applied Physics, 51(26), p.264004_1 - 264004_9, 2018/07

https://doi.org/10.1088/1361-6463/aac56b

Searching for novel spin caloric effects in antiferromagnets we study the properties of thermally activated magnons in the presence of an external spin current and temperature gradient. We predict the spin Peltier effect - generation of a heat flux by spin accumulation - in an antiferromagnetic insulator with cubic or uniaxial magnetic symmetry. This effect is related with spin-current induced splitting of the relaxation times of the magnons with opposite spin direction. We show that the Peltier effect can trigger antiferromagnetic domain wall motion with a force whose value grows with the temperature of a sample. We also demonstrate that the external spin current can induce the magnon spin Seebeck effect.

Spin-transfer torques in antiferromagnetic textures; Efficiency and quantification method

Yamane, Yuta*; Ieda, Junichi; Sinova, J.*

Physical Review B, 94(5), p.054409_1 - 054409_8, 2016/08

AA2016-0164.pdf:0.5MB

https://doi.org/10.1103/PhysRevB.94.054409

We formulate a theory of spin-transfer torques in antiferromagnets, which covers the small to large limits of the exchange coupling energy relative to the kinetic energy of the inter-sublattice electron dynamics. Our theory suggests a natural definition of the efficiency of spin-transfer torques in antiferromagnets in terms of well-defined material parameters, revealing that the charge current couples predominantly to the antiferromagnetic order parameter and the sublattice-canting moment in, respectively, the limits of large and small exchange coupling. The effects can be quantified by analyzing the antiferromagnetic spin-wave dispersions in the presence of charge current: in the limit of large exchange coupling the spin-wave Doppler shift always occurs, whereas, in the opposite limit, the only spin-wave modes to react to the charge current are ones that carry a pronounced sublattice-canting moment. The findings offer a framework for understanding and designing spin-transfer torques in antiferromagnets belonging to different classes of sublattice structures such as, e.g., bipartite and layered antiferromagnets.

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

Yamane, Yuta*; Hemmatiyan, S.*; Ieda, Junichi; Maekawa, Sadamichi; Sinova, J.*

Scientific Reports (Internet), 4, p.6901_1 - 6901_5, 2014/11

https://doi.org/10.1038/srep06901

Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient.

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

Ieda, Junichi; Yamane, Yuta*; Hemmatiyan, S.*; Sinova, J.*; Maekawa, Sadamichi

no journal, , 

We show that electric voltage generation (spinmotive force) from magnetic bubble arrays subject to a magnetic field gradient. The formula for the induced voltage is derived and whereby a new method is proposed for determining the magnitude of the phenomenological parameter that measures non-adiabaticity of current-induced magnetization dynamics. This spinmotive force opens up a door for developing a new type of spintronics devices relying on the magnetic field gradient.

Spinmotive force due to antiferromagnetic dynamics

Ieda, Junichi; Yamane, Yuta*; Sinova, J.*

no journal, , 

Recently, spintronics phenomena in antiferromagnets (AFM) attract attention. Especially spin transfer torque (STT) and spinmotive force (SMF) that have been established and play principal roles in ferromagnets become important subjects since they enable us to control and detect AFM dynamics. A few approaches have been theoretically proposed for treating these effects in AFMs but they are still under debate. In this work, we theoretically investigate SMF due to AFM dynamics by incorporating the finite canting between sublattice magnetizations, non-adiabaticity of the electron dynamics, and the Rashba spin-orbit interaction, which were all omitted in previous work. We show that the electric voltages can be generated by field-induced AFM domain wall motion and AFM resonance. This finding is useful as providing an electrical detection method of AFM dynamics and opens up the possibility of materials search for the larger SMF signals.

Electrical conductivity of antiferromagnetic Dirac quasi-particles

Yamamoto, Kei; Smejkal, L.*; Jungwirth, T.*; Sinova, J.*

no journal, ,