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Several magnetic, heat capacity and X-ray diffraction measurements are used and carried out to study the synthesis of a two-dimensional polymeric spin crossover (SCO) coordination polymer, which exhibits a two-step spin transition. The analysis shows that a decrease in the temperature results in an increase of the thermal factor, which in combination with the absence of a superstructure peaks in the diffraction pattern leads to the observed two steps disorder.

Research is presented demonstrating the combined use of an inelastic neutron scattering study with magnetic susceptibility, specific heat and magnetization measurements on a deuterated sample of K10[Co4(H2O)2(PW9O34)2].22H2O, to investigate the ground state properties of a tetranuclear Co2+ cluster.

A series of dimeric iron(II) spin-crossover [Fe(L)(NCS)2]2(bpym) compounds were synthesized by the reaction of [Fe(H2O)6] (ClO4)2 and KNCSe with a methanolic solution of bpym and methanol/dichloromethane. The dinuclear iron(II) spin-crossover compounds such as [Fe(bpym)(NCSe)2]2(bmpy) and [Fe(bt)(NCSe)2]2(bmpy) exhibited an average Fe-N bond distance of 0.2 angstrom for the high spin state. However, [Fe(bpym)(NCSe)2]2(bpym) has a shorter Fe-N bond distance compared to [Fe(bpym)(NCSe)2]2(bpym).

Magnetic susceptibility and heat-capacity measurements of [Co.sub.3][(As[O.sub.4]).sub.2] [center dot] 8[H.sub.2]O and [Ni.sub.3][(As[O.sub.4]).sub.2] [center dot] 8[H.sub.2]O have shown the existence of long range antiferromagnetic ordering at 7.1 and 8.3 K, respectively. The analysis of the measurements together with the structural features have shown a stronger ferromagnetic dimers interaction. The ordering of the Co compound has been characterized as a planar one with S=1/2 and having a three-dimensional crossover below 2 K. For the Ni compound the magnetic ordering at [T.sub.N] is three-dimensional Heisenberg with S=1.

The heat capacity of [Bi.sub.2]Cu[O.sub.4] has been measured from 5 to 350 K in an adiabatic calorimeter. A long range ordering peak was found at 42.7 K due to the establishment of three-dimensional antiferromagnetic order. The magnetic entropy calculated for the anomaly corresponds to the theoretical value for spin 1/2, [Delta] S = R ln 2, discarding the existence of any lower dimensional magnetic contribution at a higher temperature.

Adiabatic heat-capacity measurements of some of the intermetallic compounds [R.sub.2][Fe.sub.17][X.sub.y] (R = Er, Tm, Gd; X = N, D) have been performed from 5 K to 350 K. Magnetic ordering phase transitions have been observed at 291.9 K for [Er.sub.2][Fe.sub.17] and at 260 K for [Tm.sub.2][Fe.sub.17]. The anomalous enthalpy and entropy of these transitions are much smaller than expected in a pure localized model for the magnetic moments. In [Tm.sub.2][Fe.sub.17] a spin reorientation phase transition of second order character has been observed at 94 K. Theoretical calculations of the free energy and thermodynamic functions have been developed. In the interstitial compounds [Er.sub.2][Fe.sub.17][D.sub.3.4], [Tm.sub.2][Fe.sub.17][D.sub.2.13], [Gd.sub.2][Fe.sub.17][N.sub.2.18] and [Er.sub.2][Fe.sub.17][N.sub.2.4] no anomalies have been observed.

The giant magnetocaloric effect in MnAs produced by a magnetostructural first-order phase transition is studied. The spike in the isothermal entropy change is described as an artifact due to the incorrect application of the Maxwell relation to path dependent thermodynamic functions that are not state functions.

The synthesis and characterization of layered double hydroxides containing paramagnetic [Ni.sup.II] and diamagnetic/paramagnetic [Al.sup.III]/[Fe.sup.III] ions are reported. The remarkable and tunable magnetic properties of layered double hydroxide clays behaving as magnets at high temperatures could find potential application to produce hydrotalcite-like magnetic materials.

Heat capacities of the iron(III) spin crossover complex [Fe(3-MeO-salenEt).sub.2]]P[F.sub.6] are measured by using adiabatic calorimetry for mechanically unperturbed and differently perturbed samples. The mechanochemical perturbation has exerted its effect on the low-spin state than on the high-spin state and has shown a substantial increase of the number of iron(III) ions in the high-spin state below the transition temperature.

Direct determinations of the isothermal entropy increment, -△ST, in the Heusler alloy Ni50CoMn36Sn13 on demagnetization gave positive values, corresponding to a normal magnetocaloric effect. These values contradict the results derived from heat-capacity measurements and also previous results obtained from magnetization measurements, which indicated an inverse magnetocaloric effect, but showing different values depending on the technique employed. The puzzle is solved, and the apparent incompatibilities are quantitatively explained considering the hysteresis, the width of the martensitic transition and the detailed protocol followed to obtain each datum. The results show that these factors should be analyzed in detail when dealing with Heusler alloys. [ABSTRACT FROM AUTHOR]

Presents information on a study that measured the magnetic susceptibility of polycrystalline samples of cesium[sub2]copper chlorine[sub4] over the temperature interval 1.1-30 Kelvin. Experiment details; Results and discussion.