Jiunn-Yuan Lin 林俊源
Institute of Physics 交大物理所
National Chiao Tung University
Contents
 Introduction to magnetism
 Introduction to superconductivity
 The best way of measuring the magnetic
moment-SQUID!
 Specification of MPMS
Fundamentals of magnetism
 Diamagnetism
 Paramagnetism
 Ferromagnetism
 Antiferromagnetism
Diamagnetism
 Due
to Faraday’s law

dB
E  
dt


B   B  dA
Paramagnetism
 
M
B
 
C
T
 
C
T
Ferromagnetism
Antiferromagnetism
Hysteresis
Magnetic domains
To minimized the
magnetostatic energy
U 
1
 2
2
B dx
0
3
Magnetic Force Microscope (MFM)
Introduction to superconductivity
The Race to Beat Cuprates?
Hg - cuprate
TI - cuprate
150
100
？
Tc(K)
YBCO
Fe-based
superconductors
Cuprates
MgB2
LSCO
50
Nb3Ge
e-doped SmOFe
e-doped LaOFeA
e-doped LaOFeP
Metallic alloys
0
70
80
90
100
110
Year of discovery
The crusade of Room Temperature superconductors?
Josephson effect
(1962)

The
electronic
superconductors
applications
of
Speed(sec/gate)
Thermal limit
Quantum
limit
SC device
Power consumption
Speed & power consumption of SFQ device
SQUID
The SQUID
 Within
a year of Brian Josephson’s discovery,
the first Superconducting Quantum
Interference Device (SQUID) was built
 In 1968, Professor John Wheatley of UCSD
and four other international physicists founded
S. H. E. Corp. (Superconducting Helium
Electronics) to commercialize this new
technology.
SQUID Magnetometers





The first SQUID magnetometer was developed by Mike
Simmonds, Ph.D. and Ron Sager, Ph.D. while at S.H.E.
Corporation in 1976.
In 1982, Mike and Ron, along with two other SHE
employees, founded Quantum Design.
In 1984, QD began to market the next generation
SQUID magnetometer – the Magnetic Property
Measurement System (MPMS).
In 1996, QD introduced the MPMS XL as the latest
generation SQUID magnetometer
During the past 22 years, six companies have
unsuccessfully designed and marketed SQUID
magnetometers to compete with the MPMS.
MPMS XL EverCool™ System
MPMS XL Temperature Control
Patented dual impedance design allows continuous
operation below 4.2 K
 Sample tube thermometry improves temperature
accuracy and control
 Transition through 4.2 K requires no He reservoir
refilling and recycling (no pot fills)
 Temperature sweep mode allows measurements
while sweeping temperature at user controlled rate

 Increases measurement speed

Smooth temperature transitions through 4.2 K both
cooling and warming
MPMS XL Temperature Control
MPMS XL Temperature Control
MPMS XL Temperature Control
Temperature Range:
 Operation Below 4.2 K:
 Temperature Stability:
 Sweep Rate Range:
1.9 - 400 K (800 K with optional oven)
Continuous
±0.5%
0.01 - 10 K/min with smooth transitions
through 4.2 K
 Temperature Calibration ±0.5% typical
Accuracy:
 Number of Thermometers: 2 (one at bottom of sample tube; one at
the location of sample measurements)

Magnetic Field Control



Very high homogeneity magnets (1, 5 and 7 Tesla)
 0.01% uniformity over 4 cm
Magnets can be operated in persistent or driven mode
 Hysteresis mode allows faster hysteresis loop
measurements
Magnets have two operating resolutions: standard and high
resolution
Type of Magnet
1 tesla
5 tesla
7 tesla
Standard resolution
0.5 Oe 1.0 tesla
1 Oe 5.0 tesla
2 Oe 7.0 tesla
High resolution
0.05 Oe 1500 Oe
0.1 Oe 5000 Oe
0.2 Oe 6000 Oe
Hysteresis Measurement
Reciprocating Sample Measurement System
(RSO)


Improved measurement sensitivity
Increased measurement speed
 No waiting for the SQUID to stabilize
 Very fast hysteresis loops up to 8x faster than conventional
MPMS
Servo motor powered sample transport allows
precision oscillating sample motion
 High precision data acquisition electronics includes a
digital signal processor (DSP)

 SQUID signal phase locked to sample motion
 Improved signal-to-noise ration

Low thermal expansion sample rods with sample
centering feature
Reciprocating Sample Measurement System
(RSO)
RSO Data



The DC scan
took 56 hours to
take 960 points
The RSO scan
took 1600 points
in under 24
hours!
The RSO scan
avoids
subjecting the
sample to field
inhomogeneities
that effected the
DC scan.
Hysteresis Mode Data
This measurement
takes ~ 3.5 hours in
persistent mode
Reciprocating Sample Measurement System
(RSO)




Frequency Range:
0.5 - 4 Hz
Oscillation Amplitude: 0.5 - 50 mm
Relative Sensitivity:
< 1 x 10-8 emu; H  2,500 Oe,
T = 100 K(for 7-tesla magnet)
 6 x 10-7 emu; H @ 7 tesla,
T = 100 K (for 7-tesla magnet)
Dynamic range
10-8 to 5 emu (300 emu with
Extended Dynamic Range option)
0.0005
Ba(Fe1-xCox)2As2 (x=0.08) H//ab=50 Oe
FC
ZFC
0.0000
M (emu)
-0.0005
-0.0010
-0.0015
-0.0020
0
5
10
15
T (K)
20
25
30
MPMS System Options

Transverse Moment Detection
 for examining anisotropic effects
 Second SQUID detection system

Ultra-Low Field
 Reduce remanent magnet field to
±0.05 Oe

Extended Dynamic Range

External Device Control
 Control user instruments with the
MPMS

10 kBar Pressure Cell
Sample Space Oven
 Temperatures to 800 K


Environmental Magnetic Shields
Fiber Optic Sample Holder
 Allows sample excitation with
light

Manual Insertion Utility Probe
 Perform elector-transport
measurements in MPMS
 Measure moments to ±300 emu

Sample Rotators
 Vertical and Horizontal
SQUID AC Susceptibility
 2 x 10-8 emu sensitivity 0.1 Hz to
1 kHz




Liquid Nitrogen Shielded Dewar
EverCool Cryocooled Dewar
 No-Loss liquid helium dewar
 No helium transfers
SQUID AC Susceptibility

Dynamic measurement of sample
 Looks also at the resistance and conductance
 Can be more sensitive the DC measurement

Measures Real () and Imaginary () components
  is the resistance of the sample
  is the conductive part
 Proportional to the energy dissipation in the sample

Must resolve components of sample moment that is out
of phase with the applied AC field
 SQUID is the best for this because it offers a signal response that is
virtually flat from 0.01 Hz to 1 kHz


Available on all MPMS XL systems
Requires system to be returned to factory for upgrade
SQUID AC Susceptibility

Features
 Programmable Waveform Synthesizer and high-speed Analogto-Digital converter
 AC susceptibility measured automatically and can be done in
combination with the DC measurement
 Determination of both real and imaginary components of the
sample’s susceptibility
 Frequency independent sensitivity

Specifications
 Sensitivity (0.1 Hz to 1 kHz):2 x 10-8 emu @ 0 Tesla
1 x 10-7 emu @ 7 Tesla
 AC Frequency Range:
 AC Field Range:
 DC Applied Field:
0.01 Hz to 1 kHz
0.0001 to 3 Oe (system dependent)
±0.1 to 70 kOe (system dependent)
SQUID AC Susceptibility
Ultra-Low Field Capability





Actively cancels remanent field in all MPMS
superconducting magnets
Sample space fields as low as ±0.1 Oe achievable
Custom-designed fluxgate magnetometer supplied
Includes Magnet Reset
Requires the Environmental Magnet Shield
Hysteresis measurement
Extended Dynamic Range
Extends the maximum measurable moment from ±
5 emu to ± 300 emu (10 orders of magnitude)
 Automatically selected when needed in
measurement
 Effective on both longitudinal and transverse
SQUID systems

Sample Space Oven

Provides high temperature measurement
capability
 Ambient to 800 K
Easily installed and removed by the user
when needed
 A minimal increase in helium usage

 Approximately 0.1 liters liquid helium/hour

3.5 mm diameter sample space
MPMS Horizontal Rotator
Automatically rotates sample about a horizontal axis
during magnetic measurement
 360 degrees of rotation; 0.1 degree steps
 Sample platform is 1.6 X 5.8
 Diamagnetic background signal of 10-3 emu at 5 tesla

Manual Insertion Utility Probe



Perform electro-transport measurement in the MPMS
sample space
10-pin connector
Use with External Device Control (EDC) for controlling
external devices (e.g., voltmeter and current source)
 Creates fully automated electro-transport measurement system
External Device Control
Allows control and data read back from third party
electronics
 Allows custom control of MPMS electronics
 Use with Manual Insertion Utility Probe for
automated electro-transport measurements
 MPMS MultiVu version written in Borland’s Delphi
(Visual Pascal) programming language

Fiber Optic Sample Holder




Allows sample to be illuminated by an external light
source while making magnetic measurements
Optimized for near UV spectrum (180 to 700 nm)
Includes 2-meter fiber optic bundle
Sample bucket 1.6 mm diameter and 1.6 mm deep
SMA connector
Slide seal
Fiber optic bundle