As and Epitaxial-Growth MnSi Thin Films - OPUS Würzburg

84 7. Magnetotransport with H ‖ [111]
values of parameters (Figure 7.3) is at the maximum αρ xx /βρ 2 xx ≈ 0.1, which introduces
a only slight error into the extracted parameters if using the simplification from [Lee 07]
for thin samples. It can also be completely forced to be compensated by the other two
parameters, as the longitudinal resistivity is at least four orders of magnitude larger than
the (symmetrized) Hall resistance, consistent with the clean limit assumptions in [Lee 07].
Forsubsequent measurements werelyonthesimplifiedformula: ρ xy ≈ R 0 B+βρ 2 xx M+ρT xy .
Extracting the fitting parameters from high field measurements on the 20 nm layer (Figures7.4-7.6),
thecalculatedHallcoefficient R H ismeasured as≈17nΩ-cm/Tonaverage,
which is higher than the results calculated in [Lee 07].(≈ 7 nΩ-cm/T) [Neub 09b] used
a similar value for calculating the spin polarization P of the topological Hall effect at
the A-phase, however with a smaller effective field of 2.5 T than [Ritz 13a] (≈ 13T). A
possible expanation would be a reduced carrier concentration in MnSi thin films arising
0.37
0.36
0.35
R xy
(ohm)
0.34
0.33
0.32
-3000 -2000 -1000 0 1000 2000 3000
Magnetic Field (mT)
0.352
0.02
R EVEN xy (Ω)
0.348
R ODD xy (Ω)
0.00
0.344
-0.02
-3000 -2000 -1000 0 1000 2000 3000
Magnetic Field (mT)
-3000 -2000 -1000 0 1000 2000 3000
Magnetic Field (mT)
Fig. 7.4: Result from low temperature Hall measurements for 20 nm layer at a saturation
field of ±3T with countinuous field sweep rate of 30mT/min: (a) Actual measured signal with
contributions from the longitudinal component of the Hallbar, (b) The extracted Hall signal
(asymmetric) and (c) resistance corrections from the longitudinal resistance (symmetric). The
symmetric contributions arise from misalignments during the lithography process.