Successive magnetic phase transitions in high-stage MoCl ₅-graphite intercalation compounds

The magnetic phase transitions of high-stage MoCl₅-graphite intercalation compounds have been investigated by magnetic susceptibility and spontaneous magnetisation measurement in the temperature range 16 mK<or=T<or=4.2K. The experimental results show that the successive magnetic phase transitions occur at T_cl and T_cu. The upper transition temperature T_cu is not dependent on the stage number (N) of these compounds (T_cu=1.60K), which suggests that the magnetic ordering between T_cl and T_cu is two-dimensional. The lower transition temperature T_cl shifts to lower temperatures as the stage number increases from 3 to 5 (T_cl=690 mK for N=3, 500 mK for N=4 and 400 mK for N=5), which gives an evidence for the three-dimensional magnetic ordering below T_cl.