| Description |
Micron-size superconducting quantum interference devices (micro-SQUIDs), with superconducting weak links replacing the Josephson junctions, have been found useful for measuring the properties of isolated magnetic nano-structures or local magnetization on a sample surface. However, thermal hysteresis in such weak-links is an obstacle for improving micro-SQUID performance for magnetometry. In this talk I shall discuss a thermal model describing the hysteretic behavior in several experimentally studied Nb based weak links and Micro-SQUIDs in our lab. An interesting outcome of both the model and experiments is a cross-over temperature above which the hysteresis disappears. However, one gets a very narrow temperature range of hysteresis-free operation. Another method that we have investigated to eliminate hysteresis is the use of parallel shunt resistor. With this idea we have been able to get a wide temperature range of hysteresis free operation. In addition, we get a very good flux sensitivity in these non-hysteretic micro-SQUIDs.
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