2003/08/13 by Masatsugu Suzuki, Itsuko S. Suzuki
Physics and Astronomy · #cond-mat.dis-nn
paper · pdf · doi:10.1103/physrevb.69.144424
published as Phys. Rev. B 69, 144424 (2004) · 14 pages, 16 figures, and 2 tables
arxiv created 2003/08/13 · arxiv updated 2009/12/01
Linear and nonlinear dynamic properties of a reentrant ferromagnet Cu0.2Co0.8Cl2-FeCl3 graphite bi-intercalation compound are studied using AC and DC magnetic susceptibility. This compound undergoes successive phase transitions at the transition temperatures Th (= 16 K), Tc (= 9.7 K), and TRSG (= 3.5 K). The static and dynamic behaviors of the reentrant spin glass phase below TRSG are characterized by those of normal spin glass phase with critical exponent β = 0.57 ± 0.10, a dynamic critical exponent x = 8.5 ± 1.8, and an exponent p (= 1.55 ± 0.13) for the de Almeida -Thouless line. A prominent nonlinear susceptibility is observed between TRSG and Tc and around Th, suggesting a chaotic nature of the ferromagnetic phase (TRSG ≤ T ≤ Tc) and the helical spin ordered phase (Tc ≤ T ≤ Th). The aging phenomena are observed both in the RSG and FM phases, with the same qualitative features as in normal spin glasses. The aging of zero-field cooled magnetization indicates a drastic change of relaxation mechanism below and above TRSG. The time dependence of the absorption χ′ ′ is described by a power law form (≈ t^-b′ ′) in the ferromagnetic phase, where b′ ′ ≈ 0.074 ± 0.016 at f = 0.05 Hz and T = 7 K. No ωt-scaling law for χ′ ′ [≈ (ωt)^-b′ ′] is observed.