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A study was conducted to analyze the low-temperature magnetization and thermoremanence of CoCl2.H20. Thermoremanent magnetization data after cooling in smaller fields were also examined. Field-cooled and zero-field-cooled magnetization were determined versus temperature. Experimental results indicated the weakening of interchain interactions occurs in CoCl2 H20 relative tot he parent dihydrate. Findings also showed a change in regime between 2 and 3 kG.

The preparation and magnetic behavior of a peculiar pentacoordinate Fe3+ compound, which was essential for scattering measurements and neutron diffraction, were studied. This compound exhibited magnetic anisotropy, which was analogous to the normal material, and critical behavior when ferromagnetic transition took place at 2.457 Kelvin.

Magnetic susceptibility and equilibrium heat capacity measurements of polycrystalline CoCl2.H2O reveal ferro and antiferromagnetic interactions and anisotropic effects, causing two-dimensional characteristics and phase transitions in the compound. The heat capacity Cp ranges between 0.6 and 80K with an inflection point at 4.5K, resulting in the unique temperature-dependent spin glass thermoremanent magnetization.

The antiferromagnetic characteristics of powdered Fe(S2CNC4H8)2I were investigated. The results showed that most of the spin order was of a short-range low dimensional nature. A discrepancy between the doublet-doublet separations gave evidence of a possible temperature dependence of antiferromagnetism.

The magnetic characteristics of Ni(SCN)2 under low temperatures were investigated. The results showed that Ni(SCN)2 ordered antiferromagnetically at a critical temperature of 52 K. This indicated that there was no magnetic dimensionality. In addition, magnetic isotherms were linear to 16 kG with some features suggesting the occurence of lower temperature transitions.

The magnetic properties of little examined CuCl 2 ·2D 2 O are studied and compared with those of CuCl 2 ·2H 2 O. New CuBr 2 ·6H 2 O is also examined. Susceptibility maxima appear for chlorides at 5.35 and 5.50 K, in the above order, with estimated antiferromagnetic ordering at 4.15 and 4.25 K. Curie-Weiss fits yield g of 2.210 and 2.205, and Weiss θ of −6.0 and −4.7 K, respectively, in χ M = C/(T − θ). One-dimensional Heisenberg model fits to susceptibilities, including interchain exchange in a mean-field approximation, are performed. Interchain exchange is significant but much weaker than intrachain. The bromide hexahydrate strongly differs magnetically from any chloride hydrate, but exhibits notable similarities and differences compared to previously studied CuBr 2 . A broad susceptibility maximum occurs near 218 K, only 4% lower than for CuBr 2 , but with almost twice the magnitude. Powder X-ray diffraction data for CuBr 2 ·6H 2 O may be best accounted for by a monoclinic unit cell that is metrically orthorhombic. The volume per formula unit is consistent with trends in metal ionic radii. However, an alternative monoclinic cell with 5% smaller volume more readily rationalizes the magnetism. [ABSTRACT FROM AUTHOR]

Relaxation in the insulating spin glass Co1-xMnxCl2 was investigated using heat capacity and nuclear magnetic resonance measurements. The results showed that the time dependence of the thermoremanent magnetization conformed to a decay of stretched exponential type. However, small systematic deviations of data from fitted curves were observed.

Abstract: A new mixed magnet, Mn1−x Ni x Cl2·H2O, is examined by dc magnetization and susceptibility measurements across the entire composition range. The pure components are quasi-one-dimensional Heisenberg antiferromagnets ordering at 2.17K (Mn) and 5.65 K (Ni) due to weaker interchain exchange supplementing the dominant exchange along MCl2MCl2M… chemical and structural chains. High temperature magnetic susceptibilities yield Curie and Weiss constants in χ M=C/(T−θ). C(x) is linear but θ(x) displays curvature, which is analyzed to show that unlike-ion exchange is ferromagnetic and similar in size to like-ion. Most notable is the absence of antiferromagnetic susceptibility maxima down to 1.6K from x=0.10 to 0.95. For x=0.05 a susceptibility maximum appears, with T max almost 20% lower than in the pure Mn component but T c reduced by 2%. The size of the susceptibility is enhanced by admixture, the effect of disrupted antiferromagnetic tendencies. Magnetization isotherms evolve with composition. Larger values of magnetization, under the same measuring conditions, occur for mixtures than for pure components, consistent with frustration, which weakens antiferromagnetic alignment tendencies. The competing ferromagnetic (Ni) and antiferromagnetic (Mn) intrachain interactions, along with disorder and low dimensional characteristics, presumably lead to the absence of magnetic order over a remarkably broad composition range. [Copyright &y& Elsevier]

Abstract: The magnetic properties of Mn1− x Ni x Cl2·2H2O are examined by DC magnetization and susceptibility measurements on a wide range of compositions. The pure components are three-dimensional Heisenberg antiferromagnets, ordering at 6.7K (MnCl2·2H2O) and at 7.25 K (NiCl2·2H2O). Each contains MC12MC12M… chemical (and structural) chains, with intrachain exchange ferromagnetic and antiferromagnetic in the Ni and Mn materials, respectively. Interchain exchange is predominantly antiferromagnetic in each. The Curie and Weiss constants, in fits to high temperature data, vary regularly with composition. C(x) is essentially linear, and exhibits systematic curvature which is analyzed to show that unlike-ion exchange is antiferromagnetic and weaker than like-ion interactions. The form of the susceptibility evolves with composition: maxima in ) broaden and shift to lower temperature with admixture of either component, but beyond about 20% minority component such maxima are absent, with upturns appearing instead. T c descends rapidly with admixture from either composition extreme, but varies only weakly between and 0.70. Magnetization isotherms display a subtle composition dependence which suggests that the ordered state differs for intermediate compositions from those for the composition extremes. Although frustration in mixtures is likely, from competing (sign) intrachain interactions, it is not strong enough to yield magnetic irreversibilities or time dependences signaling a spin glass phase. [Copyright &y& Elsevier]

Heat capacity measurements from 0.6 to 40 K are reported for various compositions of mixed magnetic Co1−xMnxCl2·H2O. For x=0.40–0.80 only broad maxima in the heat capacity appear. For x=0.90 a sharp peak is seen, at 1.727±0.005 K, but is not ideally lambda-like, due to effects of disorder. A lattice separation is made using results from earlier analyses of the heat capacities of the pure components. The resulting C(mag) displays a better resolved but still very broad maximum, for which the size increases with increasing x while the location, Tmax, decreases. Approximately 90% of the theoretical entropy in various mixtures accumulates up to 40 K. For the x=0.40 and 0.50 mixtures significantly less than half the theoretical entropy accumulates up to Tmax. For these two compositions a linear regime in the low temperature heat capacity is apparent, below 2.4 and 2.1 K for x=0.40 and 0.50, respectively, which are taken as spin glass transition temperatures Tg. Very similar characteristic temperatures were found for the irreversible magnetization behavior in earlier work on the same mixed system. The present results show that the combined effects of disorder and frustration suppress magnetic ordering over a remarkably broad composition range in Co1−xMnxCl2·H2O. [Copyright &y& Elsevier]