  We perform a systematic X-ray analysis of six giant radio relics in four
clusters of galaxies using the Suzaku satellite. The sample includes CIZA
2242.8-5301, Zwcl 2341.1-0000, the South-East part of Abell 3667 and previously
published results of the North-West part of Abell 3667 and Abell 3376.
Especially we first observed the narrow (50 kpc) relic of CIZA 2242.8-5301 by
Suzaku satellite, which enable us to reduce the projection effect. We report
X-ray detections of shocks at the position of the relics in CIZA2242.8-5301 and
Abell 3667 SE. At the position of the two relics in ZWCL2341.1-0000, we do not
detect shocks. From the spectroscopic temperature profiles across the relic, we
find that the temperature profiles exhibit significant jumps across the relics
for CIZA 2242.8-5301, Abell 3376, Abell 3667NW, and Abell 3667SE. We estimated
the Mach number from the X-ray temperature or pressure profile using the
Rankine-Hugoniot jump condition and compared it with the Mach number derived
from the radio spectral index. The resulting Mach numbers (M=1.5-3) are almost
consistent with each other, while the Mach number of CIZA2242 derived from the
X-ray data tends to be lower than that of the radio observation. These results
indicate that the giant radio relics in merging clusters are related to the
shock structure, as suggested by previous studies of individual clusters.
