Polycrystalline Zn3N2 films are prepared on Si and quartz glass substrates by RF magnetron sputtering at room temperature. The structural and optical proper-ties are studied by X-ray diffraction and double beam spectrophotometer, respectively. X-ray diffraction indicates that the Zn3N2 films deposited on Si and quartz glass substrates both have a preferred orientation in (321) and (442), also are cubic in structure with the lattice constant a=0.9847 and 0.9783 nm, respectively. The absorption coefficients as well as the film thickness are calculated from the transmission spectra, and their dependence on photon energy is examined to determine the optical band gap. Zn3N2 is determined to be an indirect-gap semiconductor with the band gap of 2.11(2) eV. (C) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The electronic structures and atomic magnetic moments of Nin clusters (n= 2—6) have been studied. Compared with crystalline nickel, some clusters increase obviously in magnetism; some decrease obviously; and some show ferrimagnetism. The symmetry of clusters has great effect on magnetic moment. If they are similar in symmetry, the clusters are similar in magnetic moment. The magnetic moment for small clusters does not seem to increase or decrease monotonically with the change in their size, because adding or removing one atom may fully change the symmetry of small clusters. As the surface layer of ultrafine particles is made of many different polyhedrons with low symmetry and the alignment of the polyhedrons is complicated, the whole surface layer presents short-range order. The calculated results explain the abnormal phenomena about surface magnetism that have been in existence for a long time.

Intergrain interaction can be classified as the long-range magnetostatic interaction between grains and the exchange coupling interaction of neighboring grains. The strengths of interactions depends on the microstructure of the materials. The intergrain interactions can be studied and compared by the theoretical model calculation and by analyzing the experimental curves. The effects of exchange coupling interaction on the properties for nanometer soft magnetic materials and nanometer two-phase permanent magnetic materials were introduced.

The electronic structure of Nd2Fe17 has been calculated using the spin-polarized MS-Xα method based on the assumption that the FeFe and FeNd exchange couplings are dominant. The calculation showed that (i) there are three levels presenting negative exchange couplings between Fe(f) and Fe(c) atoms, and (ii) the crystal structure symmetry of the compound sometimes has a more important effect on the exchange coupling than the atomic spacing. The key factors affecting the magnetic-ordered property of R2Fe17 are discussed.

The lowest energy geometries of Morse pair potential clusters (n ≤ 40) have been determined. The minimization problem in the multi-dimensional configuration space is solved by combining the Monte Carlo method and a fast relaxation algorithm. The obtained results are identical with measured nickel cluster geometries, indicating that Ni cluster belongs to the Morse species rather than to the Lennard-Jones-like cluster. It is predicted that magic numbers of small Ni clusters may be 6, 13, 15, 19, 23, 26, 29, 32, 34, 36, 38.

The experimental results show that the coercivity of Nd-Fe-B sintermagnet decreases with increasing of the grain alignment degree of the magnets (i.e. decreasing of the orientation distribution coefficient ��). The coercivities of the magnets with different orientation degrees are calculated based on the pinning, nucleation and starting field theory, respectively. The comparison of the calculated values with the experimental results shows that the theoretical results deviate from the experiments seriously for both pinning mechanism and nucleation mechanism. In contrast with that, the calculated values based on the starting field theory are in good agreement with the experimental results.

Calculations of the magnetic domain structure (domain wall energy density, domain wall thickness, domain width and critical diameter of single domain particles) in Nd2Fe14B have been made by using its intrinsic parameters (lattice constants, magnetic moments of the atoms, Curie temperature, spontaneous magnetization and magneto-crystalline anisotropy constant). The four stages of magnetization reversal processes in oriented sintered Nd-Fe-B magnet after saturation magnetization along its easy direction are studied in detail in this paper. The results show that the nucleation of the reverse-magnetization nuclei in the surface layer of the grains of hard magnetic phase Nd2Fe14B, as well as the irreversible domain wall motion from the surface to the inside of the grains are dominant factors controlling the intrinsic coercivity of the Nd-Fe-B alloy.