As and Epitaxial-Growth MnSi Thin Films - OPUS Würzburg
As and Epitaxial-Growth MnSi Thin Films - OPUS Würzburg
As and Epitaxial-Growth MnSi Thin Films - OPUS Würzburg
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8.1. Magnetotransport Measurements in <strong>MnSi</strong> epitaxial thin films 113<br />
1.0<br />
0.8<br />
R/R B=0<br />
0.6<br />
0.4<br />
0.2<br />
0.0<br />
R PHE xx (ohm)<br />
0.36<br />
0.32<br />
0.28<br />
0.24<br />
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3<br />
Magnetic Field (T)<br />
R PHE xy (ohm)<br />
0.10<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0.20<br />
0.00<br />
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3<br />
Magnetic Field (T)<br />
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3<br />
Magnetic Field (T)<br />
Fig. 8.14: PHE curves for the 20-nm grown film with current <strong>and</strong> 0 degree magnetic field<br />
direction along <strong>MnSi</strong>[¯213] at various angles (0 to 180 degrees, 15 degree steps), including the<br />
antisymmetric <strong>and</strong> symmetric parts of the signals. The curves are shifted for clarity.<br />
strued as real signature from the spin structure in the material. The results are shown<br />
in Figures 8.14 (antisymmetric component enlarged in Figure 8.15) <strong>and</strong> 8.16. For the<br />
symmetrized results, R xx denotes the symmetric component <strong>and</strong> R xy the antisymmetric<br />
component.<br />
There is a marked difference between the extracted antisymmetric signals of the two<br />
grown films, with the component larger in the thinner layer. <strong>As</strong> for the source of this<br />
antisymmetric term, we have a few possibilities. Lithographic imperfections may introduce<br />
an asymmetry in the measured signals. <strong>As</strong>ymmetric contacts were used by groups to<br />
determine vortex chirality from the planar Hall effect, wherein the shift in the switching<br />
fields <strong>and</strong> asymmetry of the saturation signal were used to determine the h<strong>and</strong>edness of a<br />
vortex.[Huan 06] Further fabrication of asymmetric devices might be useful in determining<br />
the contribution of lithographic errors in the antisymmetric component of the PHE<br />
signals.<br />
A second explanation relies on the asymmetry of the crystalline structure of the material.<br />
The studies of [Mudu 05] on these systems propose the antisymmetric part arising<br />
from the antisymmetric part of the magnetoresistivity tensor. The antisymmetric part<br />
of the PHE signal in Fe <strong>and</strong> Fe 3 Si films grown on Ga<strong>As</strong>(113)A substrates have also been<br />
explained by the contribution of the anomalous Hall effect through the chirality of the<br />
crystal structure.[Frie 06]Iftrueforthegrownfilms, thelattercouldexplainthedifference
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