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FeII, FeIII and mixed‐valence FeII–III chlorides were reacted with poly[N,N′‐bis(dimethylsilyl)ethylenedi‐ amine], [Si(CH3)2NHCH2CH2NH]n, to form the corresponding Fe‐polycarbosilazane macromolecular complexes. The average chain–chain spacing in these materials was estimated from X‐ray diffraction data and found to be 6.94, 7.29, 7.30 and 7.45 Å in metal‐free and FeII, FeIII and FeII–III‐containing polycarbosilazanes, respectively. This demonstrates that FeII, FeIII and FeII–III chlorides are encapsulated between the polycarbosilazane chains. The chain–chain expansions in the divalent FeII and trivalent FeIII chloride macromolecular complexes are comparable, but less than that in the FeII–III chloride analog, which suggests that different chain–chain packings exist in the mixed‐valence macromolecular complex. The magnetic properties of the resulting complexes were investigated by measuring the magnetization in magnetic fields up to 8 kOe and in the temperature range from liquid nitrogen temperature to room temperature. Copyright © 2007 Society of Chemical Industry

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The DC susceptibility under zero-field-cooled and field-cooled conditions, hysteresis loop and isothermal remanent magnetization measurements have been carried out on a powdered sample of . The temperature and field dependence of the critical current density and the pinning-force density , and the irreversibility field were obtained from the hysteresis loops. An exponential-like dependence of the critical current on both temperature and applied field was observed over the temperature range 85 - 115 K in fields up to 0.6 T. The time-dependent magnetization data were analysed within the Anderson - Kim flux creep model. Derived potential barrier heights were found to increase with increasing temperature over the range 85 - 105 K.

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