Susceptibility & Transport
Fedor Balakirev – Capability Leader
Description of Capabilities
The NHMFL group transport measurements capabilities, including resistivity, Hall effect etc., at the Pulsed Magnet use facility are centered around lock-in techniques. To keep up with millisecond timescales of the magnet pulse, the typical recommended lock-in frequencies are in the range between 25 kHz and 400 kHz, depending on the sample properties.
The NHMFL group at LANL has developed custom instrumentation that provides the ability for lock-in detection of multiple physical channels of data, thus increasing throughput and efficiency of a typical pulse-field experiment, pictured below. It is particularly useful when a large number of independent measurements have to be conducted within a limited time frame, i.e., while accessing high magnetic field facilities. The data acquisition is configured in the synchronous time constant mode, where analog-to-digital conversion rate of the sample signal is an integer multiplicative of the excitation sine wave frequency, which allows for output settling time as short as single period of the excitation sine wave. To improve the multi-channel lock-in sensitivity we have also designed and built low-noise preamplifiers with a typical front-end noise figure of just 0.9 nV(Hz)1/2. The preamplifiers were tested to perform well in pulse stray magnetic field of up to 2 Tesla in the close proximity of the 85T magnet.
National High Magnetic Field Laboratory/NHMFL
Low Energy Spectroscopy