Zirconium oxynitride films were deposited onto glass and Si (1 0 0) substrates at room temperature by pulsed reactive dc magnetron sputtering of a metallic Zr target in an Ar/O2/N2 atmosphere. The structural, compositional and optical properties of the deposited films were found to depend on the ratio of nitrogen partial pressure to the total reactive gas partial pressure. Morphology investigation by atomic force microscopy showed that most of the zirconium oxynitride coatings have smooth surfaces (average roughness 2.5 nm). X-ray diffraction measurements revealed a change from the monoclinic zirconium oxide phase to the orthorhombic, and then a change to the cubic zirconium nitride phase upon changing the nitrogen content in the films. Optical properties of zirconium oxynitride films were analysed by a spectrophotometer and computer simulations. The calculated refractive index of transparent and semi-transparent films was found to be in the range 2.05–4.73 (at 650 nm). The optical band gap changed from 3.67 to 1.59 eV with changing nitrogen content. This study allows the elaboration process optimization and then the control of the film composition and properties, which is very interesting for a technological transfer.

We have investigated the volume collapse occurring in LaMnO 3 unit cell using the anisotropic Potts model modified by two types of anisotropic interactions which has been used to study the behavior of the orbitalordering configurations with temperature. The bond lengths are related to the occupation of the orbits. We have shown that the collapse is due to the change of Mn-O bonds as the temperature is raised through the transition. These results are in good agreement with the recently published experimental results.

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A study is made of an anisotropic Potts model in three dimensions where the coupling depends on both the Potts state on each site but also the direction of the bond between them using both analytical and numerical methods. The phase diagram is mapped out for all values of the exchange interactions. Six distinct phases are identified. Monte Carlo simulations have been used to obtain the order parameter and the values for the energy and entropy in the ground state and also the transition temperatures. Excellent agreement is found between the simulated and analytic results.We find one region where there are two phase transitions with the lines meeting in a triple point.The orbital ordering that occurs in LaM nO 3 occurs as one of the ordered phases.