About the Data

Important

All data parameters are available in the Original Lab Book

About this section

This section gives a documentation about the data. It explains how the data has been acquired.

The first part describes the used tools like the sensor, cryostat and instruments. Here also an overview is given over the OneNote notebook which has been used to document all measurements. This notebook contains all information about every performed measurement until m462.

Afterwards this Lab Book is continuing the measurement documentation in the second part. This is splitted into magnetic and fluctuation measurements.

Data Life Cycle

Timeline

Measurement Setup

Most of the measurements are using the gradiometry setup:

../_images/gradiometry_box.png — Fig. 9 Gradiometry Measurement Setup

Adjustable Parameters

Every parameter can have a crucial influence on the measurement. Therefore together with each measurement the corresponding used parameters are documented.

Measurement Parameters

The following parameters can be adjusted:

Parameter	Description
T	Temperature of the sample
θ	Angle between sensor and magnetic field
Type	Measurement Type (Gradio/Hloop/MFN). Determines \(I_1\) and \(I_2\)
\(I_1\)	Hall bar connection of \(I_1\)
\(I_2\)	Hall bar connection of \(I_2\)
Gate	Gate grounding (w/ one bar connection)
\(R_1\)	see Gradiometry Setup above
\(R_2\)	see Gradiometry Setup above
\(C_1\)	see Gradiometry Setup above
\(C_2\)	see Gradiometry Setup above

Magnet Parameters

Parameter	Description
\(B_{ext}\)	External field [T]
sweep	Sweeping the field?
SR	Sweeprate of the field [mT/min]
\(dB_{ext}\)	Fieldrange [T]

Lock-In Parameters

The programmable Lock-In SR830 can be used in various settings:

Parameter	Description
\(f_{ref}\)	Reference Frequency for the signal generator
\(V_{in}\)	Input Voltage
τ	Time Constant (lowpass filter)
sens	Sensitivity: Highest measurable voltage (-sens < \(V_H\) < +sens)
Float/Ground	Grounding the signal. Default: Ground
AC/DC	AC-Coupling. Default: AC
A/A-B	Input to use. Default: A-B
Reserve	Noise-Reserve. Default: Normal
Source	\(f_{ref}\) Source. Default: Internal

Noise Parameters

Signal Analyzer (SR785)

Parameter	Description
\(f_{max}\) / Freq-Span	Maximum frequency in the power spectral density
Avg	Number of averages to sample over

Pre Amplifier (SR560)

Parameter	Description
Gain Mode	Default: Low
Gain	Default: 200
Coupling	Default: AC
Output (50 Ω)	Default: LI Input A
Filters	Default: Off

Data Aquisition (DAQ)

Parameter	Description
\(f_{sample}\) / Rate	Sampling Frequency [samples / second]
Avg	Number of averages to sample over
\(f_{max}\) / Freq-Span	Maximum frequency in the power spectral density
`downsample`	Sample a part of the signal according to \(f_{sample}\)
`shifting_method`	With `downsample`
filtering signal	see SpectrumAnalyzer
`zero_padding`	Adding 0 for missing values

Todo

implement zero_padding (currently different length measurements result in data loss. See <http://gitlab.com/ody55eus/ana/-/blob/master/ana/mfn.py#L223>)

Sensor Details

This sensor is old fabicated by Merlin Pohlit. It has 3 \(\mu\) m cross size.

It has been handed to Fabrizio Porrati to grow these structures shown below

3D Nanostructures

Cryostat

Loading the sample inside Janis

Author: Mohanad
Date: 06 March 2019

Warning

We had problem when we introduced and exchange gas. The temperature was around 200K and we introduced 1mbar for 1s. The process of cooling was very fast and we lost a lot of He(l). The cooling rate was very high and we reached 4k in 1.5 hour. That was not good and we should next time wait at least one day to cool naturally and then intorduce an exchange gas.

Important

Don’t introduce exchange gas too early ( \(T > 200 K\) )
Be careful and introduce as little exchange gas as possible