U.S. Magnet lab offers new research capability: Millikelvin temperatures and high DC magnetic fields

March 1998

Contact:
Janet Patten, (850) 644-9651

TALLAHASSEE, Fla. – The National High Magnetic Field Laboratory (NHMFL) recently commissioned a research system unique in the world that offers users a combination of low temperatures and high DC magnetic fields. It is expected to be a significant advancement for numerous types of experiments including, electron transport, cantilever measurements of magnetic moment and torque, and certain magneto optic investigations.

After several years of development and testing, staff members at the NHMFL, along with colleagues at Oxford Instruments, successfully installed a portable top-loading dilution refrigerator in a 30 Tesla resistive magnet. The field range could reach 33 T by using the NHMFL's world record 33 T resistive magnet and could be extended to 45 T when the laboratory's hybrid magnet system is commissioned.

The following graph shows fractional Quantum Hall Effect data taken on a Lucent Technologies GaAs/AlGaAs high mobility heterostructure, using the new top loading dilution refrigerator for resistive magnets. The refrigerator has successfully maintained temperatures less than 30 mK at fields up to 31.5 T. The data was taken by Wei Pan, a Princeton University graduate student working at the NHMFL with Professor Dan Tsui and Dr. Horst Stormer of Lucent Technologies.

Details of interest to potential users of the new facility are:

• There are 24 sample leads as twisted pairs.
• There are 2 isolated micro-coax leads available for samples.
• None of the sample leads are needed for temperature sensors or heaters unless the experiment requires something unusual.
• There is a 0.125" diameter hole the whole length of the probe for optical fibers or other experimental requirements.
• There is no rotator currently available for this system, but one should be built by late fall.
• The sample space available for users is 14 mm. Connection to the leads is via SIPP sockets. There is an 8 pin DIPP socket sample holder available. For this sample holder, users sockets must have the corners of their sample carriers rounded so that the diagonal length across the face of the carrier is less than 0.5". Drawings of the sample space, available sample holders, and the user interface will be available at NHMFL WWW site soon.

For information and procedures for using this system, check the user facilities page or contact Bruce Brandt, Director of DC Field Facility,brandt@magnet.fsu.edu or 850-644-4068.