  We observed the northwest region of the cluster of galaxies A3667 with the
Suzaku XIS instrument. The temperature and surface brightness of the
intracluster medium were measured up to the virial radius (r200-2.3 Mpc). The
radial temperature profile is flatter than the average profile for other
clusters until the radius reaches the northwest radio relic. The temperature
drops sharply from 5 keV to about 2 keV at the northwest radio relic region.
The sharp changes of the temperature can be interpreted as a shock with a Mach
number of about 2.5. The entropy slope becomes flatter in the outer region and
negative around the radio relic region. In this region, the relaxation
timescale of electron-ion Coulomb collisions is longer than the time elapsed
after the shock heating and the plasma may be out of equilibrium. Using
differential emission measure (DEM) models, we also confirm the
multi-temperature structure around the radio relic region, characterized by two
peaks at 1 keV and 4 keV. These features suggest that the gas is heated by a
shock propagating from the center to outer region.
