Amorphous ferromagnetic materials

Hilzinger, H. R., Mager, A. Warlimont, H. (1978). Amorphous ferromagnetic materials - magnetic fundamentals, properties and applications. Journal of Magnetism and Magnetic Materials, 9, 191-9. 

In an amorphous ferromagnet (a sputtered him with the composition Tb0.33Fe0 67) Rhyne et al (1972) used neutron diffraction to demonstrate a random direction of moments with average ferromagnetic orientation. This material has a fairly sharp Curie temperature in the range 380-390 K, the moment below this temperature reaching saturation at about 50kOe. 

Mossbauer spectroscopy and NMR spectroscopy have in common that they provide information which is basically local in character. Up to now the Mossbauer effect has been more fruitfully applied to amorphous alloys than NMR. There are several reasons for this. In ferromagnetic materials the NMR can give rise to much more accurate values of the hyperfine fields than the Mossbauer effect. Owing to the extremely large line broadening this advantage is lost in amorphous alloys. 

We have a specific interest in the self-assembled structures formed by poly(ferrocenylsilane) block copolymers, such as poly(ferrocenyldimethylsilane-Z -dimethyl-siloxane) (PFS-PDMS) and (ferrocenyldimethylsilane-Z>-isoprene) (PFS-PI). The PFS block contains an iron atom in the main chain repeat unit. These polymers are particularly promising for novel applications, since they can be used as charge-transport materials and, by pyrolysis, as precursors to ferromagnetic ceramics [4-6], Moreover, they can by synthesized with a very narrow molar mass distribution, with excellent control over chain length and composition [7], An important feature of PFS is that the polymers bearing two methyl groups on the silane unit are crystalline, whereas polymers with two different substituents on each silane (methyl, ethyl methyl, phenyl) are atactic and remain amorphous. This feature of the polymer composition has a strong influence on the type of self assembled structures that these poly-... 

Several CT complexes of metal bis(arene) compounds containing, among others, the familiar organic acceptor TCNQ have been reported [71]. None of these materials has been shown to display physical properties superior to those of the metallocene systems. One very important exception is related to the reaction of bis(benzene) vanadium (which is isoelectronic with [MnCpf ]) with TCNE, which affords a material with unprecedented properties [72]. The amorphous material obtained displays bulk ferromagnetism at room temperature and its even exceeds the decomposition temperature of the sample of about 350 K. The compound is no longer an arene complex as it has an empirical composition corresponding to V(TCNE)2 1/2(CH2C12). 

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