title: Ageing dynamics of ferromagnetic and re-entrant spin glass phases in a stage-2 Cu(0.80)Co(0.20)Cl(2) graphite intercalation compound.
abstract: Ageing dynamics of a re-entrant ferromagnet stage-2 Cu(0.8)Co(0.2)Cl(2) graphite intercalation compound has been studied using DC magnetization measurements. This compound undergoes successive transitions at the transition temperatures T(c) (≈8.7 K) and T(RSG) (≈3.3 K). The relaxation rate S(ZFC)(t) exhibits a characteristic peak at t(cr) below T(c). The peak time t(cr) at constant t(w) shows a local maximum around 5.5 K, indicating a slow dynamics arising from a frustrated nature of the ferromagnetic phase. It drastically increases with decreasing temperature below T(RSG). The spin configuration imprinted at the stop and wait process at a stop temperature T(s) (<T(c)) during the field-cooled ageing protocol becomes frozen on further cooling. On reheating, the memory of the ageing at T(s) is retrieved as an anomaly of the thermoremnant magnetization at T(s). These results indicate the occurrence of the ageing phenomena in the ferromagnetic phase (T(RSG)<T<T(c)) as well as in the re-entrant spin glass phase (T<T(RSG)).
authors.affiliation: Department of Physics, State University of New York at Binghamton, Binghamton, NY 13902-6000, USA.
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Suzuki
authors.forename: Itsuko S
authors.initials: IS
authors.lastname: Suzuki