1. Cell 12 Magnet unit: mm Data Acquisition computer
Data acquisition program
Magnet control
Cell 12 Magnet
unit: mm
Magnet/Power supply status monitoring computer
35.1 T, 32 mm bore
Available cryostats: He3 (0.3 – 60 K) or VTI (1.4 – 300 K)

2. Sample holder mounted on the probe Side A Side B
System D Rotator Probe
Sample holder mounted on the probe
Side A
Side B
Before mounting
Sample holder : side A
side view
Sr2RuO4
Magnetic torque
Capacitance between the two parallel plates
top view

3. 11.4 mm Sample holder : side B SrMnBi2 Electrical transport
Resistance (Rxx)
Hall sensor (THS 118: GaAs based)
Hall Resistance (Rxy)
1.5 mm
0.25 mm
Ba2Fe2As2
Surface conductivity
TDO (Tunnel Diode Oscillator) resonance freq. shift
PdCoO2
Magnetic torque
Resistance change of piezo-resistive device

4. Triplet superconductor (Tc = 1.4 K)
Sr2RuO4
Triplet superconductor (Tc = 1.4 K)
Torque: Capacitance signal, T= 30 mK
C. Bergemann et al., Physica B 294, 371 (2001)

5. Parent compound of 122 pnictide superconductors
BaFe2As2
Parent compound of 122 pnictide superconductors
TDO frequency shift
30 mK
350 mK
D. E. Graf et al., PRB 85, (2012)
J. G. Analytis et al., PRB 80, (2009)

6. SrMnBi2
Dirac Fermion compound
SrMnBi2
CaMnBi2
J. Park et al., PRL (2011)
K. Wang et al., PRB (R) (2012)

7. PdCoO2
Metallic triangular lattice compound
Torque signal (piezo-cantilever)
T=0.7 K
C. W. Hicks et al., PRL (2012)

8. Measurement techniques
Resistance measurements by instrumentation (Rxx, Rxy, piezo-cantilever)
principle: apply current (current source) and measure voltage (voltmeter)
Conventional lock-in amplifier technique
Oscillating current applied, phase sensitive detection of corresponding voltage
DC resistance measurement technique
DC current with switching polarities to remove offset
AC resistance bridge
Resistance determined by nulling or measuring unbalanced signal
Q: what is advantage/disadvantage of the lock-in technique compared to the DC technique?
Capacitance measurement for magnetic torque
AH capacitance bridge: automatic balancing
GR capacitance bridge: manual balancing
Q: what other physical properties can be measured by the capacitance measurement device?
Typical capacitance bridge
TDO resonance frequency measurement

9. Exercises 1: Resistance measurement on the standard resistor
(hints given in the appendix)
Lock-in technique
configure resistance measurement setup with 1 lock-in amplifier (SR 830)
Change parameters (current, frequency, time constant, ..) and check the voltage readings
DC technique
Configure measurement setup with 1 DC current source (Keithley 6221) and 1 DC nanovoltmeter (Keithly 2182)
Apply constant DC current ( < 10 mA) and monitor the voltage
Setup the Delta mode and test with different parameters (current, delay time,..)
Exercises 2: Capacitance measurement on the standard capacitor
AH bridge : hook up coax cables to the decade capacitor box and press buttons
(2) GR bridge
configure GR bridge and 1 lockin-amplifer for capacitance measurement
balance the GR bridge to find the capacitance value (should be similar to obtained from (1)
find the conversion factor between lock-in signal and capacitance

10. Exercises 3: Balancing the piezo-cantilever
Build a measurement circuit with a given bridge circuit box
Balance the bridge
inside cryostat
Demonstration 1: TDO measurement
Exercises 4: Setting up instruments for the real samples
Setup instruments for the Hall sensor (DC resistance delta mode) and piezo-cantilever (lock-in technique). Refer to the breakout box diagram in the next page.
NOTE: Do not apply currents until further notice.
(2) Instructor will setup AC resistance bridge for the transport measurement
(3) Connect cables to the AH bridge for the capacitance measurement
(4) Using the data acquisition program, collect the data at zero field as a function of time

11. Exercises 5: Data acquisition
NHMFL breakout box
variable
resistor
can be used as pseudo-current source setup when combined with lock-in oscillator
Exercises 5: Data acquisition
Collect data while sweeping magnetic field under different instrumentation setup
Collect data at different temperatures
Collect data at different angles
Exercise/Demonstration: Data analysis
Plot the data using data analysis program
Q1) Plot the temperature vs. magnetic field. Why does temperature reading change with field? Any way to circumvent the problem?
Q2) What is the oscillation frequency of the quantum oscillations?
Q3) Capacitance torque signal from Sr2RuO4 sample look different from the text book (saw-tooth not sinusoidal). Why?
(2) Perform FFT with different settings (field range, different background, FFT windows, …)
(answer given in the appendix)

12. Appendix I Resistance measurement (Lock-in technique)
Oscillator out to the current terminals with a large resistor connected in series
Connect voltage terminals to voltage input (A-B mode)
osc. out
voltage input
sample
Current limiting resistor (R)
I = V/(Rsample+R) ~ V/R (if R >> Rsample)
DC resistance measurement (delta mode)
Configure Delta (picture above) : set I-high, I-low, Delay. ,,,,
Press Delta to arm
Press TRIG to start delta mode operation

13. Torque interaction analysis in Sr2RuO4 by Naoki Kikugawa
Appendix II
Torque interaction analysis in Sr2RuO4 by Naoki Kikugawa
Sr2RuO4
T = 1.4 K
B // ~ c axis
Data taken at Cell 12 (May 21, 2014)
Remember:
The oscillation is periodic in 1/B not in 1/H
Raw data
(before de-torque)
FFT: 28 – 34.5T
De-torqued
FFT: 28 – 34.5 T