We report on the dependence on field and temperature of the critical current of micro superconducting quantum interference devices (SQUIDs): SQUIDs with diameters as small as 1 μm using Dayem bridges as weak links. We model these SQUIDs by solving the Ginzburg–Landau equations with appropriate boundary conditions to obtain the supercurrent–phase relationships. These solutions show that the phase drops and depression of the order parameter produced by supercurrent flow are often distributed throughout the micro-SQUID structure, rather than being localized in the bridge area, for typical micro-SQUID geometries and coherence lengths. The resultant highly nonsinusoidal current–phase relationships Ic(φ) lead to reduced modulation depths and triangular dependences of the micro-SQUID critical currents on applied magnetic flux Ic(Φ). Our modeling agrees well with our measurements on both Al and Nb micro-SQUIDs.

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