Magnetic Phase Diagram of Three-Dimensional Diluted Ising Antiferromagnet Ni_<0.8>Mg_<0.2>(OH)_2(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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H-T diagram of 3D diluted Ising antiferromagnet Ni_cMg_<1-c>(OH)_2 with c = 0.8 has been determined from measurements of SQUID DC magnetization and AC magnetic susceptibility. At H = 0, this compound undergoes two magnetic phase transitions: an antiferromagnetic (AF) transition at the Neel temperature T_N (= 20.7 K) and a reentrant spin glass (RSG) transition at T_<RSG> (≈ 6 K). The H-T diagram consists of the RSG, spin glass (SG), and AF phases. These phases meet a multicritical point P_m (H_m = 42kOe, T_m = 5.6K). The irreversibility of susceptibility denned by δ (= X_<FC> - X_<ZFC>) shows a negative local minimum for 10 ≤ H ≤ 35kOe, suggesting the existence of possible glassy phase in the AF phase. A broad peak in δ and X" at H ≥ 20kOe for T_N(c=0.8,H) ≤ T ≤ T_N(c=1,H=0) (=26.4K) suggests the existence of the Griffiths phase.
社団法人日本物理学会の論文
2004-01-15