MAGNETIC PHASE-TRANSITIONS OF CRCL3 GRAPHITE-INTERCALATION COMPOUND

Magnetic phase transitions of stage-2 CrCl3 graphite intercalation com pound have been studied using ac superconducting quantum interference device (SQUID) magnetic susceptibility and dc SQUID magnetization. Thi s compound is a two-dimensional (2D) Heisenberg ferromagnet with small XY anisotropy and very weak antiferromagnetic interplanar exchange in teraction: interplanar exchange interaction J (=5.86+/-0.05 K), effect ive anisotropy field H-A(out)(=193 Oe), and H-E'(=51 Oe). This compoun d undergoes magnetic transitions at T-c1(=11.5 K), T-c2(=10.3-10.5 K), T-c3(=8.67-9.70 K), and T-g(=5.7-7 K). Below T-c1 a 2D ferromagnetic long-range order with spin component along the c axis appears, forming an axial ferromagnetic phase. Below T-c2 a 2D ferromagnetic long-rang e order of spin component perpendicular to the c axis appears, forming an oblique phase. Below T-c3 there appears a 3D antiferromagnetic ord er accompanying spin-glass-like behavior. Below T-g the system enters into a reentrant spin glass phase arising from the competition between a ferromagnetic Cr3+-Cr3+ interaction and possible antiferromagnetic Cr2+-Cr2+ interactions. The role of Cr2+ spins with Ising symmetry may be crucial for the axial ferromagnetic and oblique phases. [S0163-182 9(98)02218-8].