The response of high-Tc SQUID magnetometers to small changes in temperature

We have investigated the response of the flux-locked output of several high-Tc SQUID magnetometers to small changes in temperature and for magnetic fields 0–30 μT. The temperature response DT≡dΦS/dT is observed to be linear in the applied magnetic field Ba and can be as large as 500 mΦ0/K where ΦS is the flux through the SQUID loop and Φ0 is the flux quantum. Our measurements can be explained using a simple model that takes into account the geometry of a given device and is based on the idea that DT is due to the temperature dependence of the superconducting penetration depth. Our results can be used to optimize device performance in applications where the noise of a device is dominated by ambient temperature fluctuations.