Spin-glass phases in stage-2 graphite intercalation compound

The magnetic phase transitions of stage-2 (Formula presented) graphite intercalation compound have been studied using superconducting quantum interference device dc and ac susceptibility measurements in the temperature range between 1.9 and 18 K. The temperature, frequency, and field dependence of (Formula presented) and (Formula presented) clearly show that this compound undergoes two kinds of spin-glass phase transition at (Formula presented) and (Formula presented) respectively. Both (Formula presented) and (Formula presented) have peaks at (Formula presented) that shift to the low-temperature side with decreasing frequency. The spin-glass phase below (Formula presented) may result from a competition between the antiferromagnetic (Formula presented)-like (Formula presented) spins as the majority and the ferromagnetic Ising (Formula presented) spins as the minority. The absorption (Formula presented) has a peak at (Formula presented) that shifts to the low-temperature side with decreasing frequency. No anomaly in (Formula presented) is observed at (Formula presented) indicating that only the (Formula presented) components of spins contribute to this transition. The spin-glass transition below (Formula presented) may result from a competition between the intraplanar nearest-neighbor antiferromagnetic and next-nearest-neighbor ferromagnetic intraplanar exchange interaction, which is responsible for a possible incommensurate in-plane spin structure at low temperatures.