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Accueil du site > Vie du laboratoire > Congrès / Colloques / Conférences > Optical Properties of Individual Nanowires and Quantum Dots in High Magnetic Field, Septembre 2014 > Programme du workshop > Abstract : Spin splitting enhancement in ZnMnTe diluted magnetic nanowires

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Abstract : Spin splitting enhancement in ZnMnTe diluted magnetic nanowires

Spin splitting enhancement in ZnMnTe diluted magnetic nanowires

 

P. Wojnar1*, E. Janik1,2 , J. Suffczyński2, J. Papierska 2, P. Kossacki 2, M. Szymura1,
W. Zaleszczyk, S.
Kret1 Ł. Kłopotowski1, T. Wojciechowski1, L. T. Baczewski1,
G.
Karczewski1, T. Wojtowicz1, J. Kossut1

 

1 Institute of Physics, Polish Academy of Sciences, Al Lotników 32/46, 02-668 Warsaw, Poland

2Institute of Experimental Physics, University Warsaw, ul Hoża 69, 00-681 Warsaw, Poland

 

 

Incorporation of transition metal ions into semiconductor nanowires should considerably affect spin-related properties of carriers confined inside of these structures. In particular, an enhancement of the spin splitting arising from sp-d exchange interaction between the band carriers and magnetic ions is expected to occur, as already well-established in the studies of diluted magnetic bulk crystals [1]. These effects would broaden the possible application range of nanowires by including spintronic devices, such as spin filters or nanosensors of magnetic molecules.

 

In this work we will present our recent progress in the growth and studies of telluride nanowires fabricated in a molecular beam epitaxy (MBE) process employing a vapor-liquid-solid (VLS) growth mechanism [2]. In the first part, activation of optical transitions in the near band edge emission region of ZnTe nanowires by embedding them into ZnMgTe coating shells will be presented [3,4]. The main role of the shells is the passivation of ZnTe nanowire surface states. Moreover, the impact of the tensile strain acting on the ZnTe nanowire cores arising from the lattice mismatched shells will be discussed [5]. The main part of the presentation will be devoted to properties of ZnTe nanowires containing a small molar fraction of magnetic Mn-ions and on the resulting giant spin splitting of excitonic levels present in these structures [3].

 

In micro-PL measurements, when the size of the excitation laser spot is reduced down to 2 μm, the relatively broad near band edge emission from the nanowire ensemble splits into several 3-5 meV wide lines related to the emission from individual nanowires. The dependence of the spectral position of these lines on the magnetic field can be well fitted with a Brillouin function, which clearly demonstrates that the origin of this energy shift is the sp-d exchange interaction. From these fits the Mn content inside individual nanowires is obtained and does not vary significantly from nanowire to nanowire grown in the same process.

 

The most important aspect of this work is that we clearly and directly proved that nanowires with the key characteristics of diluted magnetic semiconductors, i.e., with strong sp-d coupling determining new magnetic properties, can be grown by MBE with the use of VLS mechanism.

 

The research has been supported by the European Union within European Regional Development Fund through Innovative Economy grant (POIG.01.01.02-00-008/08), National Centre of Science (Poland) grant DEC-2011/01/D/ST5/05039

 

[1] "Introduction to the Physics of Diluted Magnetic Semiconductors" edited by Gaj J. A. ; Kossut, J, Springer Series in Material Science 144,2010

[2] Janik E et al., Appl. Phys. Lett, 2006, 89 133114

[3] Wojnar P et al., Nano Lett., 2012, 12, pp 3404–3409

[4] Wojnar P et al., Nanotechnology, 2013, 24, 365201

[5] Wojnar P et al., Appl. Phys. Lett. 2014, 104, 163111

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*Contact : wojnar@ifpan.edu.pl