Details

Autor(en) / Beteiligte

• Tesařová, N.
• Němec, P.
• Rozkotová, E.
• Zemen, J.
• Janda, T.
• Butkovičová, D.
• Trojánek, F.
• Olejník, K.
• Novák, V.
• Malý, P.
• Jungwirth, T.

Titel

Experimental observation of the optical spin–orbit torque

Ist Teil von

• Nature photonics, 2013-06, Vol.7 (6), p.492-498

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2013

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Electrical and optical control of magnetization are of central importance in the research and applications of spintronics. Non-relativistic angular momentum transfer or relativistic spin–orbit coupling provide efficient means by which electrical current driven through a ferromagnet can exert a torque on the magnetization. Ferromagnetic semiconductors like (Ga,Mn)As are suitable model systems with which to search for optical counterparts of these phenomena, where photocarriers excited by a laser pulse exert torque upon magnetization. Here, we report the observation of an optical spin–orbit torque (OSOT) in (Ga,Mn)As. The phenomenon originates from spin–orbit coupling of non-equilibrium photocarriers excitated by helicity-independent pump laser pulses, which do not impart angular momentum. In our measurements of the time-dependent magnetization trajectories, the signatures of OSOT are clearly distinct from the competing thermal excitation mechanism, and OSOT can even dominate in (Ga,Mn)As materials with appropriately controlled micromagnetic parameters. A novel non-thermal photomagnetic torque originating from spin–orbit coupling of non-equilibrium photocarriers excited by helicity-independent laser pulses is found in (Ga,Mn)As thin films. It differs fundamentally from optical spin–transfer torque. The possibility of studying spin–orbit torques on short timescales achievable by pump–probe magneto-optical measurements is demonstrated.