Magnetic ordering and crystal structure in selected transition- metal compounds

Abstract: Applications of magnetic materials are inherently related to their crystal, magnetic and electronic structures. In this thesis, experimental and theoretical methods have been focused on magnetic bulk materials from novel chemical synthesis, to X-ray diffraction for initial phase characterisation, and crystal and magnetic structure studies to explain their complex magnetic properties. A selection of materials was studied, ranging from 3d transition-metal phosphides to rare-earth transition-metal intermetallics. Several techniques (including X-ray and neutron diffraction, magnetisation measurements,Mössbauer spectroscopy and first principles, electronic structure calculations) were combined to obtain a unified picture.In the (Fe1-xCox)3P compounds (x<0.37), a dependence of structure and ferromagnetic properties on Co concentration was demonstrated. The situation for the (Fe1-xMnx)3P system is more complex and has been studied at both ends of the composition range. At the Fe-rich end (x<0.25), the compounds exhibit ferromagnetic ordering, while at the Mn-rich end (x≥0.67), an antiferromagnetic coupling was discovered. The majority of the experimental results are supported by theoretical calculations.Magnetic ordering in the TbNi5-xCux system was determined, starting with the incommensurate modulated helimagnetic structure for the binary compound TbNi5, and going over to the collinear ferromagnetic structure for the Cu-substituted pseudo-binary system.The phase stability investigation of CePt2Sn2 was made using in situ X-ray powder diffraction with respect to tetragonal and monoclinic modifications. The crystal structures were determined by the Rietveld refinement method.