  The spontaneous flux generation and magnetic field modulation of the critical
current in a 0-pi Josephson junction are calculated for different ratios of the
junction length to the Josephson penetration depth, and different ratios of the
0-junction length to the pi-junction length. These calculations apply to a
Pb-YBCO c-axis oriented junction with one YBCO twin boundary, as well as other
experimental systems. Measurements of such a junction can provide information
on the nature of the c-axis Josephson coupling and the symmetry of the order
parameter in YBCO. We find spontaneous flux even for very short symmetric 0-pi
junctions, but asymmetric junctions have qualitatively different behavior.
