Structural and magnetic properties in Mn-doped GaN grown by metal organic chemical vapor deposition Appl. Phys. Lett. 92, 152116 (2008); 10.1063/1.2909545 Anomalous magnetic properties of the ferrimagnetic semiconductor on Ga-doped sulphur spinel

Articles you may be interested inAbove room-temperature ferromagnetism of Mn delta-doped GaN nanorods Appl. Phys. Lett.Ferromagnetic behavior of GaN doped with Mn (Ga 1Ϫz Mn z N) grown by the ammonothermal and chemical transport methods is discussed in terms of a second phase ͑ferromagnetic one͒ produced during the growth process. The reference manganese nitride samples grown by the same method as ͑Ga,Mn͒N reveal room-temperature ferromagnetic behavior, depending on the growth details. Different Mn x N y phases are suggested to be responsible for ferromagnetic behavior of ͑Ga,Mn͒N.

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Application of the in situ high pressure powder diffraction technique for examination of specific structural properties of nanocrystals based on the experimental data of SiC nanocrystalline powders of 2-30 nm in diameter is presented. Limitations and capabilities of the experimental techniques themselves and methods of diffraction data elaboration applied to nanocrystals with very small dimensions (<30 nm) are discussed. It is shown that a unique value of the lattice parameter cannot be determined for such small crystals using a standard powder diffraction experiment. It is also shown that, due to the complex structure constituting a two-phase, core/surface shell system, no unique compressibility coefficient can satisfactorily describe the behaviour of nanocrystalline powders under pressure. We offer a tentative interpretation of the distribution of macro-and micro-strains in nanoparticles of different grain size.

Fundamental limitations, with respect to nanocrystalline materials, of the traditional elaboration of powder diffraction data like the Rietveld method are discussed. A tentative method of the analysis of powder diffraction patterns of nanocrystals based on the examination of the variation of lattice parameters calculated from individual Bragg lines (named the “

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Abstract. A series of "virtual powder diffraction experiments" was made on models of small single crystals and nanocrystals with the core-shell structure. The results of those experiments were elaborated with application of standard methods of data analysis routinely used for reciprocal and real space analyses of polycrystalline materials. It is shown that the assumption of a uniform crystal structure of nano-materials is not justified and, therefore, application of routine procedures of collection and elaboration of diffraction data may lead to misinterpretation of the experiments and to incorrect conclusions about their structure. Tentative ways of using powder diffraction data to learn about the structure of nanocrystals with different atomic architecture of the core and of the surface of the grains are discussed. A need for elaboration of a model of the atomic structure of an individual nanograin with a non-uniform structure is discussed. An alternative approach to diffraction studies of nanocrystals by presenting the "footprints" of materials under study in the form of plots showing distribution of the experimental apparent lattice parameters as a function of diffraction vector Q, or bond length distribution as a function of r-distances derived from PDF function is suggested.