Abstract
The stage-2 CoCl2 graphite intercalation compound behaves magnetically like a quasi-two-dimensional XY-like ferromagnet with avery weak antiferromagnetic interplanar exchange interaction. This compound undergoes two magnetic phase transitions atTcl ( = 6.8-7.2 K) and Tcu ( = 8.9 K). TheSQUID AC magnetic susceptibility at a fixed AC frequency (f = 1 Hz) has been measured as a function of AC magnetic fieldstrength h (1 mOe⩽h⩽4.2 Oe), temperature T(1.9⩽T⩽12 K) and external magnetic field (0⩽H⩽1 kOe). The dispersion (Θ1'/h) andabsorption (Θ1''/h) are stronglydependent on h for h>50 mOe in the vicinity of Tcland Tcu, whereΘ1'/h = χ1' + 3χ3'h2/4 + ··· and Θ1''/h = χ1'' + 3χ3''h2/4 + ···. We find(i) a shift of Tcl in χ1'' to thelow-temperature side with decreasing frequency and (ii) a positive local maximum in χ3' at 7.3 K. Theseresults are indicative of a re-entrant spin-glass-like phase belowTcl, where the AF phase and spin-glass phasecoexist. A positive broad peak of χ3' around8.4-8.9 K shows the occurrence of two-dimensional ferromagnetic orderbelow Tcu. The H-T phase diagram is also determinedfor H along the c plane.
Published Version
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