  We report the detection of multiple components of X-ray emission from the two
FR-II radio galaxies 3C 223 and 3C 284, based on new XMM-Newton observations.
We attribute the detected X-ray emission from the lobes of both sources to
inverse-Compton scattering of cosmic microwave background photons. With this
model, we find that the magnetic field strength in the lobes is at the
equipartition value for 3C 284, and within a factor of two of the equipartition
value for 3C 223. We also detect group-scale hot atmospheres around both
sources, and determine temperatures and pressures in the gas. The lobes of both
sources are in pressure balance with the hot-gas environments, if the lobes
contain only the synchrotron-emitting particles and the measured magnetic field
strength. The core spectra of both sources contain an unabsorbed soft
component, likely to be related to the radio jet, and an additional heavily
absorbed power-law component. 3C 223 also displays a bright (EW ~ 500 eV) Fe
K-alpha emission line.
