Magnetic phase transitions of graphite intercalation compound

Magnetic phase transitions of stage-2 (Formula presented) graphite intercalation compound have been studied using ac superconducting quantum interference device (SQUID) magnetic susceptibility and dc SQUID magnetization. This compound is a two-dimensional (2D) Heisenberg ferromagnet with small (Formula presented) anisotropy and very weak antiferromagnetic interplanar exchange interaction: interplanar exchange interaction (Formula presented) effective anisotropy field (Formula presented) and (Formula presented) This compound undergoes magnetic transitions at (Formula presented) and (Formula presented) Below (Formula presented) a 2D ferromagnetic long-range order with spin component along the (Formula presented) axis appears, forming an axial ferromagnetic phase. Below (Formula presented) a 2D ferromagnetic long-range order of spin component perpendicular to the (Formula presented) axis appears, forming an oblique phase. Below (Formula presented) there appears a 3D antiferromagnetic order accompanying spin-glass-like behavior. Below (Formula presented) the system enters into a reentrant spin glass phase arising from the competition between a ferromagnetic (Formula presented) interaction and possible antiferromagnetic (Formula presented) interactions. The role of (Formula presented) spins with Ising symmetry may be crucial for the axial ferromagnetic and oblique phases.