M. Matsuura

Ordering process in CoCl2-Graphite intercalation compound

Abstract Magnetic susceptibility and spontaneous magnetization without external field of CoCl 2 -graphite intercalation compound reveal successive transitions at T cu and T cl . The heat capacity shows an anomaly only at T cu . The characteristic temperature dependences of these quantities across the temperatures are discussed. The external field effects are also examined.

Crystallographic, thermal and magnetic properties of CoCl2-graphite intercalation compound — a quasi-two-dimensional system of finite size clusters

Abstract From the susceptibility and heat capacity measurements, the second stage CoCl 2 -graphite intercalation compound (GIC) is proved a good example of a two-dimensional XY-like ferromagnet. It is directly revealed by electron microscopy that each CoCl 2 plane is not extended infinitely but composed of many island-like clusters of finite size. The importance of the latter is discussed and it is concluded that the characteristic lattice structure is responsible to the successive nature of ordering in the present system.

Magnetic phase transitions in NiCl2-graphite intercalation compound

Abstract Magnetic phase transitions in second-stage NiCl 2 -graphite intercalation compound are investigated by magnetic susceptibility, magnetization and specific heat measurements. The experimental results show that there occur two successive magnetic phase transition at T cl = 18.0 K and T cu = 21.3 K.

Successive transition and the dynamical aspects in a quasi-two-dimensional system of finite size clusters: CoCl2-graphite intercalation compound

Abstract Succesive transitions of CoCl 2 -Graphite Intercalation Compound (CoCl 2 -GIC), a quasi two dimentsional (2D) system composed of finite size clusters, are investigated. Dynamical aspects of the transitions are examined in experiments on complex susceptibility χ ★( ω ) at ultralow frequencies, relaxation process of magnetization and temperature dependence of remnant magnetization Mr in series of heating and cooling processes.

Magnetic phase transition of CrCl3-GIC

Magnetic ordering of stage-3 CrCl3-GIC is investigated by thermoremanent magnetization Mr, ac susceptibility x′ and nonlinear magnetization M′3ω measurements. Mr indicates a single phase transition at Tc of a spin glass type, but x′ and M′3ω reveal two anomalies, suggesting a possibility of another transition below Tc.

Anomalous critical phenomena of a randomly diluted series Mn(1−x−y)Znx>Mgy (HCOO)2 ⋯ 2H2O

Abstract A series of randomly diluted mixtures Mn (1−x−y) Zn x Mg y (HCOO) 2 ⋯ 2H 2 O is investigated near the transition temperature. An anomalous critical phenomenon is found: the peak of susceptibility and heat capacity appears at two successive temperatures while in the pure system Mn(HCOO) 2 · 2H 2 O it does so only at T N .

Dynamical critical phenomena of staggered mode in Co(HCOO)2·2H2O

Abstract A critical slowing down is observed on the staggered mode in an antiferromagnetic Co(HCOO) 2 ·2H 2 O. The characteristic frequency of the dispersion is lowest ( ≈ 20 MHz) at T N . Another low frequency dispersion mode appears below T N . These characteristic dynamical features are attributable to the non-uniform ordered structure in the present system.

Phase transition of two dimensional Heisenberg antiferromagnet of S = 12

Abstract From the analysis of the susceptibility of Cu(HCOO)·4H2O in which the Cu2+ ions are on two inequivalent sites, the staggered susceptibility of a two-dimensional Heisenberg antiferromagnet is examined. From the results, and from proton NMR and heat capacity on the related salts, characteristic features of the phase transition of a two-dimensional Heisenberg antiferromagnet are inferred.