Measurement of penetration depth of MgB$_{2}$ using DC SQUID

Penetration depth is an important parameter for the design of Rapid Single Flux Quantum (RSFQ) circuits. For MgB$_{2}$, different values from 40 nm to 150 nm have been reported by different groups. We have measured the penetration depth of MgB$_{2}$ using MgB$_{2}$ DC SQUIDs. The SQUID was made using MgB$_{2}$/MgO/MgB$_{2}$ Josephson junctions with epitaxial MgB$_{2}$ electrodes deposited via Hybrid Physical-Chemical Vapor Deposition. The MgO was deposited by RF Magnetron Sputtering of an MgO target. The device shows good voltage modulation above 150 $\mu$V. The working temperature for these SQUIDs ranges from below 10K to 37K, with the optimum voltage modulation near 35K. The results will be discussed in comparison to the penetration depth reported by other measurement techniques.