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Opeil Laboratory Resources

 
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Opeil Lab's facilities in Higgins 130 include a Quantum Design Physical Property Measurement System (PPMS) with a temperature range of 2 < T < 350 K and a bi-directional 9 Tesla superconducting magnet.  This "nature friendly" cryogenic equipment comes with an EverCool Low-Loss Dewar, He4 cryogenic re-condenser and a Windows-based control computer system.  The user defined sequence-based programs allow for continuous operation utilizing a variety of experimental probes designed for a particular thermodynamic measurements.  In addition to the cryogenic refrigerator, the laboratory has a resonant ultrasound spectrometer capable of measuring elastic constants in materials as a function of temperature.

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To learn more about Quantum Design cryogenic equipment and measurement techniques, please visit this web site:  Quantum Design Web site.

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Current Measurement Capability

ACTransport

The alternating current (AC) transport puck assemblies support four transport property measurement techniques: AC Resistivity (with 360° sample rotation with/without magnetic field), 5 wire AC Hall Effect, I-V curve and critical current. AC transport provides an adjustable frequency input to ensure high accuracy with two available independent channels which measure multiple samples in a single sequence. To protect delicate samples, input current, voltage and power can be limited by the user.  Periodic calibrations are performed by a built-in series of precision resistors. 

To learn more about QD ACTransport, click here:  Electro-Transport

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Thermoelectrics Transport

The QD PPMS thermal transport system measures thermal conductivity, k, or the ability of a material to conduct heat, by monitoring the temperature drop along the sample as a known amount of heat passes through the sample. The Seebeck coefficient, S, is measured as an electrical voltage drop that accompanies a temperature drop across the material. The QD PPMS thermal transport system performs these two measurements simultaneously by monitoring both the temperature and voltage drop across a sample as a heat pulse is applied to one end. Following the measurement of k and S, the system measures electrical resistivity, r, (the reciprocal of electrical conductivity, s,) by using a standard four-probe AC resistivity technique.  From these three measurements the "thermoelectric figure of merit," ZT, can be calculated.  Often ZT, which is related to conversion efficiency, is the quantity of interest when investigating thermoelectric materials.

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To learn more about QD thermoelectric transport, click here: Thermal Transport

Cantilever Magnetometry

The QD rotator platform probe enables torque and force magnetometry using thin (5 micron) silicon cantilever magnetometers.  This technique provides an accurate measurement of a sample's bulk magnetic moment as a function of temperature and can promptly determine sudden changes in magnetization, often related to a paramagnetic to ferromagnetic (or antiferromagnetic) transition.

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To learn more about the QD Torque Magnetometer, click here: Magnetometry

Resonant Ultrasound at Low Temperatures

This user designed probe enables measurement of elastic moduli on samples with cubic and hexagonal crystal symmetry over the temperature range 5 < T < 350 K.  The resonant ultrasound technique utilizes sound waves (50 – 5 MHz) to excite the resonant frequencies of a sample material. Changes in elastic moduli across a temperature interval indicate phase transitions within the crystal structure.

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To learn more about Quasar International RUSpec and the capabilities of resonant ultrasound spectrometry, visit this web site: RUSpec Web site

Dilatometry

This technique measures the length change in a sample over changes in temperature and magnetic field (5-350 K, 0-9 T). This dilatometer made of OFHC copper utilizes a capacitive technique that compares a capacitor gap to the expansion or contraction of a sample. Further design details of this dilatometer can be found in G. Schmiedeshoff, et al., Rev. of Sci. Inst. 77, 123907 (2006) (see below). This technique enables measurement of linear and volumetric coefficients of expansion, Grüenisen parameters and indications of sudden changes in crystal symmetry.

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