Laser-induced torques in metallic ferromagnets

Freimuth, Frank; Blügel, Stefan; Mokrousov, Yuriy

doi:10.1103/physrevb.94.144432

Cited by 52 publications

(52 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, recent theories for IFE predict that light absorption plays an important role to induce spin and orbital magnetization3436. We argue that IFE should be treated as B -field for short optical pulse because the IFE-induced magnetization is an equilibrium property.…”

Section: Resultsmentioning

confidence: 82%

Optical-helicity-driven magnetization dynamics in metallic ferromagnets

2017

View full text Add to dashboard Cite

Recent observations of switching of magnetic domains in ferromagnetic metals by circularly polarized light, so-called all-optical helicity dependent switching, has renewed interest in the physics that governs the interactions between the angular momentum of photons and the magnetic order parameter of materials. Here we use time-resolved-vectorial measurements of magnetization dynamics of thin layers of Fe, Ni and Co driven by picosecond duration pulses of circularly polarized light. We decompose the torques that drive the magnetization into field-like and spin-transfer components that we attribute to the inverse Faraday effect and optical spin-transfer torque, respectively. The inverse Faraday effect is approximately the same in Fe, Ni and Co, but the optical spin-transfer torque is strongly enhanced by adding a Pt capping layer. Our work provides quantitative data for testing theories of light–material interactions in metallic ferromagnets and multilayers.

show abstract

Section: Resultsmentioning

confidence: 82%

Optical-helicity-driven magnetization dynamics in metallic ferromagnets

2017

View full text Add to dashboard Cite

show abstract

“…Compared to the frozen spin-spiral approach [15,16] such a formulation has the advantage that it becomes easier to investigate the relationship to spintronic and spincaloritronic effects. For example, the Berry phase theory of DMI allows us to relate DMI to the spin-orbit torque [4], to ground-state spin-currents [7], and to ground-state energy currents which need to be subtracted in order to extract the inverse thermal spin-orbit torque [6]. Similarly, torques due to the exchange interaction need to be considered in the theory of thermally induced spintransfer torques [17], and a Green's function expression of exchange is well suited for this purpose.…”

Section: Introductionmentioning

confidence: 99%

Geometrical contributions to the exchange constants: Free electrons with spin-orbit interaction

2017

Self Cite

View full text Add to dashboard Cite

Using thermal quantum field theory we derive an expression for the exchange constant that resembles Fukuyama's formula for the orbital magnetic susceptibility (OMS). Guided by this formal analogy between the exchange constant and OMS we identify a contribution to the exchange constant that arises from the geometrical properties of the band structure in mixed phase space. We compute the exchange constants for free electrons and show that the geometrical contribution is generally important. Our formalism allows us to study the exchange constants in the presence of spin-orbit interaction (SOI). Thereby, we find sizable differences between the exchange constants of helical and cycloidal spin spirals. Furthermore, we discuss how to calculate the exchange constants based on a gauge-field approach in the case of the Rashba model with an additional exchange splitting and show that the exchange constants obtained from this gauge-field approach are in perfect agreement with those obtained from the quantum field theoretical method.

show abstract

“…To our knowledge, all previous analysis of GaMnAs consider the bulk response [9, 10, 16, 22]. The optical response of metallic systems has also recently been studied theoretically [23, 24]. These previously considered semiconductor and metallic bulk systems naturally lack Rashba spin-orbit coupling.…”

Section: Introductionmentioning

confidence: 99%

“…The torque along the M × M × L is due to an effective field along the M × L direction. This torque is identified as the optical spin transfer torque [9, 24], and is odd in L and even in M .…”

Section: Introductionmentioning

confidence: 99%

“…Ref. [24] uses density functional theory and a Keldysh Green’s function approach to compute the components of the optical torque as a function of lifetime broadening for bulk Co, Fe, and FePt. They find the torque associated with the inverse Faraday effect is generally larger than the optical spin transfer torque for Co and FePt, but that the two components are comparable for Fe.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical spin transfer and spin-orbit torques in thin-film ferromagnets

Lǐ

Haney

2017

Phys. Rev. B

View full text Add to dashboard Cite

We study the optically induced torques in thin film ferromagnetic layers under excitation by circularly polarized light. We study cases both with and without Rashba spin-orbit coupling using a 4-band model. In the absence of Rashba spin-orbit coupling, we derive an analytic expression for the optical torques, revealing the conditions under which the torque is mostly derived from optical spin transfer torque (i.e. when the torque is along the direction of optical angular momentum), versus when the torque is derived from the inverse Faraday effect (i.e. when the torque is perpendicular to the optical angular momentum). We find the optical spin transfer torque dominates provided that the excitation energy is far away from band edge transitions, and the magnetic exchange splitting is much greater than the lifetime broadening. For the case with large Rashba spin-orbit coupling and out-of-plane magnetization, we find the torque is generally perpendicular to the photon angular momentum and is ascribed to an optical Edelstein effect.

show abstract

Laser-induced torques in metallic ferromagnets

Cited by 52 publications

References 50 publications

Optical-helicity-driven magnetization dynamics in metallic ferromagnets

Optical-helicity-driven magnetization dynamics in metallic ferromagnets

Geometrical contributions to the exchange constants: Free electrons with spin-orbit interaction

Optical spin transfer and spin-orbit torques in thin-film ferromagnets

Contact Info

Product

Resources

About