Laser control of magnetization of bulk (Zn,Mn)Te

Le Van Khoi 1Andrei Avdonin 1Robert R. Gałązka 1Michael Lentze 2Christian Kehl 2Jean Geurts 2Melanie Eyring 2Georgy Astakhov 2Volfgang Ossau 2

1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
2. Universitat Würzburg, Experimentelle Physik III, Am Hubland, Würzburg D-97074, Germany

Abstract

There is an intense search for techniques of magnetization control in MBE-grown semimagnetic semiconductors ((Zn,Mn)Se, (Cd,Mn)Te) by means other than magnetic field. We report the way for the control of the magnetization of bulk (Zn,Mn)Te. We demonstrate that by tuning the intensity of laser illumination at a constant magnetic field, the magnetization of the (Zn,Mn)Te crystals could be decreased by 60%.

(Zn,Mn)Te crystals were grown by the high pressure Bridgman method. The Zeeman effect was used to find out the sample magnetization (M). In zero magnetic field the increase of the excitation intensity (P) from 10 to 200 mW practically does not change the peak energy of the exciton, donor-acceptor pair (DAP), and intra-Mn PL emission, but strongly increases the intensity of these bands. At P > 200 mW, the exciton band shows a red shift which reaches 5 meV at P=1.2 W. These findings indicate that there is a direct energy transfer from the photocarriers to the band states and Mn ions subsystem. We have found that at a given field a relatively small increase of the excitation intensity causes a large blue-shift of the exciton line indicating a strong suppression of the Zeeman splitting, i.e. the magnetization decreases. For example, at B=6 T the ratio M(600mW)/M(10mW)=0.4. Comparing the free exciton shifts from the PL and reflectance spectra as a function of magnetic field, we found that in the (Zn,Mn)Te crystals the Mn ion system is being heated under even smallest laser excitation density. The Mn-spin temperature was deduced from the Zeeman splitting, and found to be 5.06 K at P=10 mW while the lattice temperature was kept at 1.7 K. Moreover, for a given laser excitation the heating of Mn ions system causes a strong increase in the intra-Mn and the integrated DAP PL intensities with increasing magnetic field.

 

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium F, by Le Van Khoi
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 19:17
Revised:   2009-06-07 00:44