Thu 17 Sept 2009
First angle calibration using Hall effect
- Field held at 0.2 T, measured V_H and I at various angles. Fridge at 4K.
Hall res plotted v rotator angle readout
parallel to field =~ 138 deg
perpendicular to field =~ 226 deg
delta theta = 88 deg (scaling factor --> may be due to error in controller readout due to high resistance of Mn wires)
- Rotator angle callibration using hall effect: (black line = sine curve fit)
- Hall effect angle callibration offset so 0 deg = parallel, and Hall resistance in Ohms:
Nice graph; Suggestion -use jpgs, not bmp if possible.-- AlexHamilton
- 17 Sep 2009
Fri 18 Sept 2009
Fridge cooled to base by Oleh.
Ashwin did measurements at different tilt angles, using 10nA constant current.
- SdH data 1T: 140 deg and 138 deg:
- Rotator was operated in active feedback mode so angle was held constant (otherwise rotator drifts)
- All runs were done at MC temp ~100mK
- Rotator static voltage was kept at V0 = 0.5V
- Field was swept at 0.2T/min (too fast?) up to 1 T
- All data can be found in: N:/Ashwin/Hall Effect Laphangs Sample/18-9-09 1T SdH runs
Mon 21 Sep 2009
- Theta measured from Hall effect (sin-1 Rmax/R) vs Theta set:
- got slope of 1.02 for uncorrected data as expected...
- The correction was made by assuming series resistance of 215 ohms (due to Mn wiring) in each of the 3 sensing lines. This results in a slope of 1.004...
- 21 Sep 2009
Wed 23 sep 2009
No active feedback here either
Thurs 24 Sep 2009
QHE at 8T:
Rxy at different angles is plotted vs perpendicular B
(except first trace at 138 deg - because Bperp ~ 0)
Hall resistance v B at different angles:
( For the Hall data above, I suspect that the perpendicular trace was taken at a much lower temperature, or without active feedback, or both? Because the spin split plateaus are actually clearest there. Aswin? -- AlexHamilton
- 29 Sep 2009 )
yes...you're right, there was no active feedback for the last perp trace, so the temp was probably ~40mK. For the other traces active feedback was on, T ~90mK
- 29 Sep 2009
Hmm. That means one should not put the two datasets in the same graph without making it clear that they are at different temperatures. It makes it harder to show that the oncreasing in-plane field is strengthening the spin splitting.
It would be interesting to go back to this sample one day and figure out what the electron temperature is with and without active feedback on. -- AlexHamilton
- 29 Sep 2009
Fri 25 Sep 2009
Hall effect used for angle callibration again, this time done with labview:
according the the above fit:
parallel = 138.1, perpendicular = 225.5
delta Theta = 87.5 deg
According to this fit, parallel = ~138.3
- 25 Sep 2009
Updates on angle calibration and drift
for updates on the angle calibration and drift