Magneto-optisches Schalten lokalisierter Spins in (Ga,Mn) As

• Applicant: Privatdozent Dr. Georgy Astakhov
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2009 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 111472372

• Final Report Year: 2011

Final Report Abstract

It has been demonstrated that shining light on (Ga,Mn)As ferromagnetic semiconductor results in a reduction of coercivity. This photocoercivity effect (PCE) is caused by the presence of domain wall (DW) pinning sites whose pinning efficiency decreases in light. Using strongly focused light pulses of appropriate power and duration it is possible to selectively address single DW pinning sites and switch them between pinning and depinning configurations. The depinning time was observed to drastically depend on illumination power. It changes by more than seven orders of magnitude when power is varied between 5 and 50 μW. The modeling of photoinduced DW propagation is in a quantitative agreement with experimental data. Laser switching of magnetization by the discovered photocoercivity effect in (Ga,Mn)As is a fast and extremely efficient way of writing magnetic information: a single 100 fs 0.08 nJ pulse is sufficient to cause 97% reduction in the coercive field. This compares very favourably with the efficiency of current hard drives which require about 8 nJ of energy per bit written. Such a concept of low-power magneto-optical recording can be applied to room temperature recording media consisting of magnetically soft clusters coupled to a magnetically hard layer. Clusters of diluted magnetic semiconductors can serve as programmable DW pinning sites, controlling the remagnetization processes in the hard layer. Furthermore, a novel way of producing (Ga,Mn)As ferromagnetic semiconducting thin films on non-GaAs substrates has been developed, enabling to control the strain conditions and thereby the magnetic anisotropy of (Ga,Mn)As films.

Publications

• “Non-thermal photocoercivity effect in a low doped (Ga,Mn)As ferromagnetic semiconductor”. International Symposium Spin Waves, St. Petersburg, Russia, 2009
  G. V. Astakhov
  
• “Nonthermal photocoercivity effect in a low-doped (Ga,Mn)As ferromagnetic semiconductor”. Phys. Rev. Lett. 102, 187401 (2009)
  G. V. Astakhov, H. Hoffmann, V. L. Korenev, T. Kiessling, J. Schwittek, G. M. Schott, C. Gould, W. Ossau, K. Brunner, and L. W. Molenkamp
  
• “Photomagnetism in (Ga,Mn)As ferromagnetic semiconductor”. International workshop on Ultrafast Laser Control of Spins in Nanomagnets, Nijmegen, The Netherlands, 2009
  G. V. Astakhov
  
• “Single pJ-pulse switching of magnetization in ferromagnetic (Ga,Mn)As”. Appl. Phys. Lett. 97, 232503 (2010)
  A. H. M. Reid, G. V. Astakhov, A. V. Kimel, G. M. Schott, W. Ossau, K. Brunner, A. Kirilyuk, L. W. Molenkamp, and Th. Rasing
  
• “Magnetic anisotropy in lifted-off (Ga,Mn)As thin films”. Appl. Phys. Lett. 98, 231903 (2011)
  F. Greullet, L. Ebel, F. Münzhuber, S. Mark, G. V. Astakhov, T. Kießling, C. Schumacher, C. Gould, W. Ossau, K. Brunner, W. Ossau and L. W. Molenkamp
  
• “Photo-induced Barkhausen effect in the ferromagnetic semiconductor (Ga,Mn)As”. Phys. Rev. Lett. 104, 037204 (2011)
  G. V. Astakhov, J. Schwittek, G. M. Schott, C. Gould, W. Ossau, K. Brunner, and L. W. Molenkamp
  
• “Photocoercivity effect in (Ga,Mn)As ferromagnetic semiconductors”. Ioffe Institute, St. Petersburg, Russia, 2011
  G. V. Astakhov
  
• “Photomagnetism in (Ga,Mn)As ferromagnetic semiconductor”. Moscow International Symposium on Magnetism, Russia, 2011
  G. V. Astakhov
  
• “Photomagnetism of diluted magnetic semiconductors”. Workshop on Novel Trends in Optics and Nanostructures, Augustow, Poland, 2011
  G. V. Astakhov
  
• “Spin optics in Mn-doped GaAs”. Johannes Kepler University, Linz, Austria, 2011
  G. V. Astakhov