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Abstract

We describe a second sound detector based on the observation of temperature-dependent magnetization changes in paramagnetic materials. The sensitive element consists of a small pill of powdered paramagnetic salt placed in a region of high magnetic field and surrounded by a superconducting pickup loop connected to a SQUID magnetometer. At 10 Hz, the ac sensitivity was estimated to be 3×10–9 K/radicHz, increasing to 1×10–10 K/radicHz for dc signals. The device is particularly useful for experiments near the lambda point, which can be approached much more closely than with superleak transducers.

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