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Coherent magnetic semiconductor nanodot arrays.

Wang Y, Xiu F, Wang Y, Zou J, Beyermann WP, Zhou Y, Wang KL - Nanoscale Res Lett (2011)

Bottom Line: In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors.Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility.The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia Campus, Brisbane QLD 4072, Australia. y.wang4@uq.edu.au.

ABSTRACT
In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors. Up to now, lack of reliable methods to obtain high-quality MnGe nanostructures with a desired shape and a good controllability has been a barrier to make these materials practically applicable for spintronic devices. Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility. Magnetotransport experiments reveal that the nanodot arrays possess giant magneto-resistance associated with geometrical effects. The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation.

No MeSH data available.


Related in: MedlinePlus

Magnetotransport measurements for the MnGe nanodot arrays. (a) the temperature-dependent resistivity (lnρ versus T-1) and the inset displays the plot of lnρ versus T-1/4. (b) Temperature-dependent MR under fixed magnetic fields of 5 and 10 Tesla and the inset showing the plot of ln(MR) vs T-1/3. (c) Positive MRs at different temperatures and different magnetic fields.
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Figure 4: Magnetotransport measurements for the MnGe nanodot arrays. (a) the temperature-dependent resistivity (lnρ versus T-1) and the inset displays the plot of lnρ versus T-1/4. (b) Temperature-dependent MR under fixed magnetic fields of 5 and 10 Tesla and the inset showing the plot of ln(MR) vs T-1/3. (c) Positive MRs at different temperatures and different magnetic fields.

Mentions: where ρ(T) is the temperature-dependent resistivity; ρ0 and T0 denote material parameters, α is a dimensionality parameter: α = 2 for one-dimensional (1D), α = 3 for 2D, and α = 4 for 3D systems. In order to reveal the carrier transport mechanisms at different temperature regions, fittings were performed in the plots of lnρ as a function of T-α (Figure 4a). The best fittings were found when α equals to 1 and 4 in the high-temperature and low-temperature regions, respectively, corresponding to the carrier transport via the band conduction [36] (thermal activation of acceptors) and the 3D Mott's variable range hopping processes [35]. According to the fitting results to Equation 1, the obtained nanodot arrays show a dominated hopping process below 10 K. At such a low temperature, the majority of free holes are recaptured by the acceptors. As a result, the free-hole band conduction becomes less important and hole hopping directly between acceptors in the impurity band contributes mostly to the conductivity [36]. Above 100 K, the conduction is dominated by the thermal activation of the holes (the band conduction). A thermal activation energy (Ea) of 15 meV can be obtained from Equation 1 with α = 1 and Ea = T0KB, where KB is the Boltzmann constant. This activation energy does not correspond to any known acceptor energy levels due to Mn doping in Ge, consistent with results shown in reference [20].


Coherent magnetic semiconductor nanodot arrays.

Wang Y, Xiu F, Wang Y, Zou J, Beyermann WP, Zhou Y, Wang KL - Nanoscale Res Lett (2011)

Magnetotransport measurements for the MnGe nanodot arrays. (a) the temperature-dependent resistivity (lnρ versus T-1) and the inset displays the plot of lnρ versus T-1/4. (b) Temperature-dependent MR under fixed magnetic fields of 5 and 10 Tesla and the inset showing the plot of ln(MR) vs T-1/3. (c) Positive MRs at different temperatures and different magnetic fields.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211181&req=5

Figure 4: Magnetotransport measurements for the MnGe nanodot arrays. (a) the temperature-dependent resistivity (lnρ versus T-1) and the inset displays the plot of lnρ versus T-1/4. (b) Temperature-dependent MR under fixed magnetic fields of 5 and 10 Tesla and the inset showing the plot of ln(MR) vs T-1/3. (c) Positive MRs at different temperatures and different magnetic fields.
Mentions: where ρ(T) is the temperature-dependent resistivity; ρ0 and T0 denote material parameters, α is a dimensionality parameter: α = 2 for one-dimensional (1D), α = 3 for 2D, and α = 4 for 3D systems. In order to reveal the carrier transport mechanisms at different temperature regions, fittings were performed in the plots of lnρ as a function of T-α (Figure 4a). The best fittings were found when α equals to 1 and 4 in the high-temperature and low-temperature regions, respectively, corresponding to the carrier transport via the band conduction [36] (thermal activation of acceptors) and the 3D Mott's variable range hopping processes [35]. According to the fitting results to Equation 1, the obtained nanodot arrays show a dominated hopping process below 10 K. At such a low temperature, the majority of free holes are recaptured by the acceptors. As a result, the free-hole band conduction becomes less important and hole hopping directly between acceptors in the impurity band contributes mostly to the conductivity [36]. Above 100 K, the conduction is dominated by the thermal activation of the holes (the band conduction). A thermal activation energy (Ea) of 15 meV can be obtained from Equation 1 with α = 1 and Ea = T0KB, where KB is the Boltzmann constant. This activation energy does not correspond to any known acceptor energy levels due to Mn doping in Ge, consistent with results shown in reference [20].

Bottom Line: In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors.Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility.The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia Campus, Brisbane QLD 4072, Australia. y.wang4@uq.edu.au.

ABSTRACT
In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors. Up to now, lack of reliable methods to obtain high-quality MnGe nanostructures with a desired shape and a good controllability has been a barrier to make these materials practically applicable for spintronic devices. Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility. Magnetotransport experiments reveal that the nanodot arrays possess giant magneto-resistance associated with geometrical effects. The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation.

No MeSH data available.


Related in: MedlinePlus