  We present experimental studies of high quality underdamped 0, pi, and 0-pi
ferromagnetic Josephson tunnel junctions of intermediate length L (lambda_J < L
< 5 lambda_J, where lambda_J is the Josephson penetration depth). The junctions
are fabricated as Nb/Al_2O_3/Cu_40Ni_60/Nb
Superconductor-Insulator-Ferromagnet-Superconductor heterostructures. Using
microwave spectroscopy, we have investigated the eigenfrequencies of 0, pi, and
0-pi Josephson junctions in the temperature range 1.9K...320mK. Harmonic,
subharmonic and superharmonic pumping is observed in experiment, and the
experimental data are compared with numerical simulations. Escape rate
measurements without applied microwaves at temperatures T down to 20mK show
that the width of the switching current histogram decreases with temperature
and saturates below T=150mK. We analyze our data in the framework of the short
junction model. The differences between experimental data and theoretical
predictions are discussed.
