Characterisation of advanced metal particle recording media pigments

Advanced metal particle (MP) pigments used in high density digital storage applications on flexible substrates have been characterised using a wide range of techniques. We have examined the chemical composition of the particles and find that the core consists of an iron–cobalt alloy in a structure BCC, analogous to that of α-Fe. Surface layers on the particle used to provide oxidation resistance, have been found to contain some form of oxides of Co, Al and Y as well as iron oxide which we find to be in a spinel form. From Mössbauer spectroscopy we have determined the proportion of the iron atoms in the oxide layer and find that by controlling the percentage of Y in the surface, a much thinner oxide layer results with a corresponding increase in the overall saturation magnetisation. From high resolution TEM images we have determined the particle size of each sample and compared those values with those obtained from X-ray line broadening. We find that in each case the X-ray ‘size' is about a quarter of the physical size excluding the oxide layer. This indicates the polycrystalline character of the particles and the crystallite size is in broad agreement with the activation volume of magnetisation reversal determined from an analysis of magnetic viscosity in the materials. These results are indicative of incoherent magnetisation reversal in the particles which may account for the lower than expected coercivity values in such pigments.     

Spin fluctuctuation phenomena in small particle magnetic systems: A Mössbauer spectroscopic study of collective excitations and superparamagnetic relaxation in haemosiderin

Mössbauer spectra obtained from a sample of the iron-storage protein haemosiderin have been analysed in both the collective excitation and superparamagnetic relaxation temperature regions. The results indicate that the low temperature spectra cannot be explained in terms of collective excitations, and that there must be other effects leading to the observed distribution of hyperfine fields.     

Mössbauer spectroscopy,electron microscopy and electron diffraction studies of small particle magnetic systems: Identification of disease specific haemosiderins

Mössbauer spectroscopy has shown that the iron-containing cores of the biological iron storage material haemosiderin produced under normal and various pathological conditions are significantly different in their magnetic properties. The differences have been correlated with information on the particle size, morphology, crystallinity and mineral form of the haemosiderin cores obtained by complementary electron microscopy and electron diffraction studies. These results have important implications for the use of Mössbauer spectroscopy in determining the properties of small particle magnetic systems and also considerable relevance for the improved understanding and treatment of iron overload disease.     

Complexes containing the unit Rh2 P PM (M = Cr or Mn, P P = bis(diphenylphosphino) alkane); the independence of the metal centres

Treatment of (η⁵-C₅H₅)₂Rh₂(CO)η¹-Ph₂P(CH₂)_n PPh₂(μ-η¹:η¹-CF₃C₂CF₃) (I) with (η⁵-CH₃C₅H₄)Mn(CO)₂(thf) or Cr(CO)₅(thf) gives the hetero-trinuclear products (η-C₅H₅)₂Rh₂(CO)(μ-CF₃C₂CF₃)μ:η¹:η¹-Ph₂P(CH₂)_nPPh₂(η-CH₃C₅H₃C₄)Mn(CO₂) (II, n = 1–4) and (η⁵-C₅H₅)₂Rh₂(CO)(μ-CF₃C₂CF₃)μ:η¹:η¹-Ph₂P(CH₂)nPPh₂Cr(CO)₅ (IV, n = 1–4) in good yields. In these products, the configuration of the CO and bisphosphine units on the Rh-Rh bond is trans. Related reactions between (η⁵:η⁵-C₅H₄CH₂C₅H₄)Rh₂(CO)η¹-Ph₂P(CH₂)nPPh₂(μ-η¹:η¹- (V) and the same solvated manganese and chromium complexes give (η⁵:η⁵-C₅H₄CH₂C₅H₄)Rh₂(CO)(μ-CF₃C₂CF₃)μ:η¹:η¹-Ph₂P(CH₂) (VI, n = 1, 2 or 4) and (η⁵:η⁵-C₅H₄CH₂C₅H₄)Rh₂(CO)(μ-CF₃C₂CF₃)μ:η¹:η¹-Ph₂P(CH₂) (VIII). The complexes (VI) and (VIII) have a mutually cis arrangement of CO and the bisphosphine on the Rh-Rh bond. Attempts to induce the complexes (IV), (V), (VI), and (VIII) to form clusters by loss of CO and Rh-M bond formation were not successful. Treatment with trimethylamine oxide or sunlight irradiation generally resulted in loss of the hetero-metal and formation of the dirhodium phosphine oxide complexes (III, n = 2 or 4) and (VII, n = 2, 3).     

Performance analysis of different methods to determine 131I in water samples for environmental monitoring

Journal of Radioanalytical and Nuclear Chemistry - There are different standard procedures to measure 131I concentration in water samples. For environmental monitoring purposes the best...     

Faux-boolean algebras and classical models

A certain substructure of the lattice of projections on a Hilbert space is defined, and it is shown under what conditions such a structure can be said to have a classical model (in a sense made precise). The results have implications for the interpretation of quantum mechanics.     

Faux-boolean algebras,classical probability,and determinism

It is possible to define, for any quantum system, an algebra of definite-valued events—those events that are definitely occurrent or non-occurrent. It is shown that two different sets of constraints on the algebra of definite-valued events are each equivalent to the definition of that set as a certain pseudo-Boolean algebra.