Jiunn-Yuan Lin 林俊源 Institute of Physics 交大物理所 National Chiao Tung University

Contents Introduction to magnetism Introduction to magnetism Introduction to superconductivity Introduction to superconductivity The best way of measuring the magnetic moment-SQUID! The best way of measuring the magnetic moment-SQUID! Specification of MPMS Specification of MPMS

Fundamentals of magnetism Diamagnetism Diamagnetism Paramagnetism Paramagnetism Ferromagnetism Ferromagnetism Antiferromagnetism Antiferromagnetism

Diamagnetism Due to Faraday’s law Due to Faraday’s law

Paramagnetism

Ferromagnetism

Antiferromagnetism

Hysteresis

Magnetic domains To minimized the magnetostatic energy

Magnetic Force Microscope (MFM)

Introduction to superconductivity

70 Nb 3 Ge MgB 2 Metallic alloys LSCO YBCO TI - cuprate Hg - cuprate Cuprates e-doped LaOFeP e-doped LaOFeAs e-doped SmOFeAs Fe-based superconductors The Race to Beat Cuprates? The crusade of Room Temperature superconductors? ？

Josephson effect (1962) The electronic applications of superconductors

Power consumption Speed & power consumption of SFQ device Quantum limit Thermal limit SC device Speed(sec/gate)

SQUID

The SQUID Within a year of Brian Josephson’s discovery, the first Superconducting Quantum Interference Device (SQUID) was built 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. 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 The first SQUID magnetometer was developed by Mike Simmonds, Ph.D. and Ron Sager, Ph.D. while at S.H.E. Corporation in In 1982, Mike and Ron, along with two other SHE employees, founded Quantum Design. 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 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 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. 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 Patented dual impedance design allows continuous operation below 4.2 K Sample tube thermometry improves temperature accuracy and control Sample tube thermometry improves temperature accuracy and control Transition through 4.2 K requires no He reservoir refilling and recycling (no pot fills) 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 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 Smooth temperature transitions through 4.2 K both cooling and warming

MPMS XL Temperature Control

Temperature Range: K (800 K with optional oven) Temperature Range: K (800 K with optional oven) Operation Below 4.2 K: Continuous Operation Below 4.2 K: Continuous Temperature Stability: ±0.5% Temperature Stability: ±0.5% Sweep Rate Range: K/min with smooth transitions Sweep Rate Range: K/min with smooth transitions through 4.2 K through 4.2 K Temperature Calibration ±0.5% typical Accuracy: Temperature Calibration ±0.5% typical Accuracy: Number of Thermometers: 2 (one at bottom of sample tube; one at Number of Thermometers: 2 (one at bottom of sample tube; one at the location of sample measurements) the location of sample measurements)

Magnetic Field Control Very high homogeneity magnets (1, 5 and 7 Tesla) Very high homogeneity magnets (1, 5 and 7 Tesla)  0.01% uniformity over 4 cm Magnets can be operated in persistent or driven mode 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 Magnets have two operating resolutions: standard and high resolution

Hysteresis Measurement

Reciprocating Sample Measurement System (RSO) Improved measurement sensitivity Improved measurement sensitivity Increased measurement speed 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 Servo motor powered sample transport allows precision oscillating sample motion High precision data acquisition electronics includes a digital signal processor (DSP) 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 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 DC scan took 56 hours to take 960 points The RSO scan took 1600 points in under 24 hours! 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. 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: Hz Frequency Range: Hz Oscillation Amplitude: mm Oscillation Amplitude: mm Relative Sensitivity: < 1 x emu; H  2,500 Oe, Relative Sensitivity: < 1 x emu; H  2,500 Oe, T = 100 K(for 7-tesla magnet) T = 100 K(for 7-tesla magnet)  6 x emu; 7 tesla,  6 x emu; 7 tesla, T = 100 K (for 7-tesla magnet) T = 100 K (for 7-tesla magnet) Dynamic range to 5 emu (300 emu with Dynamic range to 5 emu (300 emu with Extended Dynamic Range option) Extended Dynamic Range option)

MPMS System Options Transverse Moment Detection Transverse Moment Detection  for examining anisotropic effects  Second SQUID detection system SQUID AC Susceptibility SQUID AC Susceptibility  2 x emu sensitivity 0.1 Hz to 1 kHz Ultra-Low Field Ultra-Low Field  Reduce remanent magnet field to ±0.05 Oe Extended Dynamic Range Extended Dynamic Range  Measure moments to ±300 emu External Device Control External Device Control  Control user instruments with the MPMS 10 kBar Pressure Cell 10 kBar Pressure Cell Sample Rotators Sample Rotators  Vertical and Horizontal Sample Space Oven Sample Space Oven  Temperatures to 800 K Environmental Magnetic Shields Environmental Magnetic Shields Fiber Optic Sample Holder Fiber Optic Sample Holder  Allows sample excitation with light Manual Insertion Utility Probe Manual Insertion Utility Probe  Perform elector-transport measurements in MPMS Liquid Nitrogen Shielded Dewar Liquid Nitrogen Shielded Dewar EverCool Cryocooled Dewar EverCool Cryocooled Dewar  No-Loss liquid helium dewar  No helium transfers

SQUID AC Susceptibility Dynamic measurement of sample Dynamic measurement of sample  Looks also at the resistance and conductance  Can be more sensitive the DC measurement Measures Real (  ) and Imaginary (  ) components 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 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 Available on all MPMS XL systems Requires system to be returned to factory for upgrade Requires system to be returned to factory for upgrade

SQUID AC Susceptibility Features Features  Programmable Waveform Synthesizer and high-speed Analog- to-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 Specifications  Sensitivity (0.1 Hz to 1 kHz):2 x Tesla 1 x Tesla 1 x Tesla  AC Frequency Range: 0.01 Hz to 1 kHz  AC Field Range: to 3 Oe (system dependent)  DC Applied Field: ±0.1 to 70 kOe (system dependent)

SQUID AC Susceptibility

Ultra-Low Field Capability Actively cancels remanent field in all MPMS superconducting magnets Actively cancels remanent field in all MPMS superconducting magnets Sample space fields as low as ±0.1 Oe achievable Sample space fields as low as ±0.1 Oe achievable Custom-designed fluxgate magnetometer supplied Custom-designed fluxgate magnetometer supplied Includes Magnet Reset Includes Magnet Reset Requires the Environmental Magnet Shield 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) Extends the maximum measurable moment from ± 5 emu to ± 300 emu (10 orders of magnitude) Automatically selected when needed in measurement Automatically selected when needed in measurement Effective on both longitudinal and transverse SQUID systems Effective on both longitudinal and transverse SQUID systems

Sample Space Oven Provides high temperature measurement capability Provides high temperature measurement capability  Ambient to 800 K Easily installed and removed by the user when needed Easily installed and removed by the user when needed A minimal increase in helium usage A minimal increase in helium usage  Approximately 0.1 liters liquid helium/hour 3.5 mm diameter sample space 3.5 mm diameter sample space

MPMS Horizontal Rotator Automatically rotates sample about a horizontal axis during magnetic measurement Automatically rotates sample about a horizontal axis during magnetic measurement 360 degrees of rotation; 0.1 degree steps 360 degrees of rotation; 0.1 degree steps Sample platform is 1.6 X 5.8 Sample platform is 1.6 X 5.8 Diamagnetic background signal of emu at 5 tesla Diamagnetic background signal of emu at 5 tesla

Manual Insertion Utility Probe Perform electro-transport measurement in the MPMS sample space Perform electro-transport measurement in the MPMS sample space 10-pin connector 10-pin connector Use with External Device Control (EDC) for controlling external devices (e.g., voltmeter and current source) 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 control and data read back from third party electronics Allows custom control of MPMS electronics Allows custom control of MPMS electronics Use with Manual Insertion Utility Probe for automated electro-transport measurements Use with Manual Insertion Utility Probe for automated electro-transport measurements MPMS MultiVu version written in Borland’s Delphi (Visual Pascal) programming language 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 Allows sample to be illuminated by an external light source while making magnetic measurements Optimized for near UV spectrum (180 to 700 nm) Optimized for near UV spectrum (180 to 700 nm) Includes 2-meter fiber optic bundle Includes 2-meter fiber optic bundle Sample bucket 1.6 mm diameter and 1.6 mm deep Sample bucket 1.6 mm diameter and 1.6 mm deep Slide seal Fiber optic bundle SMA connector