  The magnetization measurements of CexLa1-xRu2Al10 (x = 1, 0.75) under the
high magnetic field were performed in order to obtain the information for the
long-range order (LRO) in CeRu2Al10. We successfully obtained the magnetic
phase diagram of these two compounds for the applied magnetic field along the
a-axis which is the magnetization easy axis, and found that the LRO for x = 1
disappears at ~50 T which is the critical field to the paramagnetic phase. For
x = 0.75, the critical magnetic field decreases to ~37 T by La substitution.
The magnetic phase diagram and magnetization curve are qualitatively consistent
with the recent Hanzawa's mean field calculation results obtained by assuming
the dimer of Ce ions whose crystalline electric field ground state has a large
magnetic anisotropy. These results support the singlet pair formation scenario
recently proposed by Tanida et al.. We also pointed out the possibility of the
appearance of the field-induced magnetic phase between ~40 T and ~50 T for x =
1.
