The magnetic structureof a55mol% Fe0-46 molyo P,O, semiconducting glass containing various relative concentrations of FeS+ and Fez+ has been studied by ESR techniques over the temperature range -190 to 300 "C. It was determined that the iron ions in the glass matrix are antiferromagnetically coupled in FeS+-Fe2+ ion pairs. The isolated Fe3+ ions were found to be in orthorhombic crystalline fields with 1 = 1/3 and 0.23 < D < 0.8 cm-l, where D and 1 are constants in the spin Hamiltonian. Heat treatment of the glass samples caused precipitation of Fes+-rich crystalline phases, and it was determined that the Fe*+ ions in these phases were antiferromagnetically aligned.

The ac and dc characteristics of 55 mol% Fe0-45 mol% P105 glass were measured as functions of time of heat treatment at 600" and of the ratio Fe3i/Feto+nl. The dc resistivity behavior a t constant temperature (for bulk spscimens) was correlated with the appearance and growth of crystals in a glassy matrix, as indicated by data obtained with a GuinierDe Wolff X-ray camera. Dispersions appeared in plots of tan S, , vs frequency; a hypothesis explaining the appearance of these peaks is presented.

No abstract

The magnetic properties and microstructures of the vanadium phosphate glass system over the composition range 60 to 90 m o % V,O, were investigated to study magnetic ordering in the glass and the effect of microstructure on its magnetic properties. Direct antiferromagnetic coupling between V" ions in the glassy matrix exists, and a transition temperature near -70°C was observed. As-cast glasses with high V,O, concentrations separated into two glassy phases; this separation increased the ESR line width as a result of inhomogeneity broadening. The separation, which concentrated the vanadium ions in a vanadium-rich phase, caused a hysteresis in the plot of ESR line intensity vs temperature at the transition temperature. Reduction of the vanadium ions by dextrose added to the melt enhanced phase separation and resulted in weak antiferromagnetic transitions a t +70° and -120°C, the Nee1 temperatures of VO, and V,O,, respectively.

Abstract. Ba(H2PO4)2, space group Pccn, a = 7.7962 (10), b = 10.2574 (10), c = 8.5653 (ll) A at 295 K (2 = 1.54051 A), Z = 4, D x = 3.212, D m = 3.21 g cm -3. A corrugated network of hydrogenbonded phosphate groups lies parallel to the ac plane with Ba--O coordination bonds running between the phosphate layers. The eight Ba-O distances range from 2.659 (2) to 2.903 (2) A. The phosphate distances are: P-OH 1.579 (2) and 1.576 (2) A, and P-O 1.495 (2) and 1.490 (2) A. Introduction.Colorless rhombic platelets of Ba(H2PO4) 2 were grown by slow evaporation from a solution of 10 g of barium phosphate in 200 g of a 10% aqueous solution of H3PO 4. The space group, Pccn, is indicated by mmm Laue symmetry with systematic absences for Okl and hOl (l odd) and hkO (h + k odd). Crystal density was measured by flotation in a mixture of tetrabromoethane and diiodomethane.The data crystal was cut to 0.5 × 0.45 × 0.45 mm and mounted on a four-circle automated diffractometer with ~0 approximately along [320]. Cell constants were determined by least-squares fit from 20, 09 and Z values measured with the resolved Cu Ktq line for 25 reflections in the range 73 ° < 20 < 88 °. Intensity data