Introduction to the NHMFL Pulsed Field Facility at LANL

Information on the physical set-up of pulsed field measurements

Read about lock-in amplifiers and their role in your measurements

Information about noise and ways to eliminate it from your measurements

How to collect and evaluate your measurement data

Information on optical spectroscopy

Information about time-resolved optics

Information on de Haas van Alphen Effect measurements

Information on Shubinkov de Haas Effect measurements

Information on Absolute Resistivity measurements

Information on Heat Capacity measurements

Information on RF Penetration Depth measurements

de Haas-van Alphen Effect

Associated Scientist: Neil Harrison <> or (505) 665-3200

The de Haas-van Alphen effect occurs in very clean metallic systems, typically in strong magnetic fields exceeding several tesla. These oscillations in the magnetization result from a phenomenon known as ``Landau quantization" whereby the electrons in a metal exist only as a series of orbitally quantized states in a magnetic field. Because the number of occupied Landau levels changes with the magnetic field, on sweeping the magnetic field one observes oscillations in the magnetization which are periodic in an inverse magnetic field.

While de Haas-van Alphen measurements are more often measured in static magnetic field using sensitive ac modulation techniques, the use of pulsed magnetic fields enables one to investigate specific phenomena that might take place in exceptionally strong magnetic fields of order 30 tesla and above. However, because metals that most readily yield de Haas-van Alphen oscillations are usually very good metals, samples need to be made very small in order to avoid the effects of eddy current heating.

The de Haas van Alphen pulsed magnetic field set-up in Los Alamos has been engineered to accommodate samples that can fit within a 400 micrometer hole, and measurements can be conducted in nearly all the magnets. This is the dimension of the inner bore of a concentrically wound pair of detection coils that are used to measure the oscillatory induced voltage during a pulse. The small size together with concentric geometry also helps combat problems associated with vibrational and/or electrical noise during the pulse. By using 10 micrometer thick insulated copper wire, approximately 500 pick-up coil windings paked-in within 200 micrometers of the inner bore. By using a custom built amplifier, we can both compensate-out the background remnant magnetic field in addition to amplifying the induced voltages by gains of up to 50,000.