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dc.contributor.advisorAttfield, John
dc.contributor.advisorRobertson, Neil
dc.contributor.authorJi, Kunlang
dc.date.accessioned2020-06-19T12:23:19Z
dc.date.available2020-06-19T12:23:19Z
dc.date.issued2020-06-25
dc.identifier.urihttps://hdl.handle.net/1842/37161
dc.identifier.urihttp://dx.doi.org/10.7488/era/462
dc.description.abstractThe thesis compiles the synthesis and study of several new materials in the perovskite and corundum families. These transition-metal oxide materials have been structurally characterised and their physical properties have been examined. The new series of substituted Dion-Jacobson layered perovskites (CuCl)La1–xSrxNb2O7 with x = 0, 0.1 and 0.2 has been prepared via topotactic ion-exchange reactions. Refined powder synchrotron diffraction data confirms that all of these compounds adopt the Pbam orthorhombic structure above room temperature and the lattice parameter a becomes larger with increasing substitution of Sr2+. The Pbam (<500 K) - Pbmm (500 - 640 K) - P4/mmm (>640 K) phase transitions found in (CuCl)LaNb2O7 that have been published in a previous report shift towards room temperature as x increases. The magnetisation data suggests that the transition to the spin dimer ground state, present in (CuCl)LaNb2O7 at 14.5 K, is fully suppressed upon Sr2+ substitution. Low temperature neutron diffraction data indicates that substituted (CuCl)La1-xSrxNb2O7 phases are paramagnetic and retain the Pbam structure down to 2 K. New corundum derivatives Co2ScSbO6 and Ni2-xCoxScSbO6 solid solutions that are of interest as potential multiferroic materials have been synthesised. Ni2-xCoxScSbO6 (x = 0 – 1.5) was prepared via a conventional solid-state route at ambient pressure while Co2ScSbO6 was synthesised under high-pressure condition as the pure phase cannot be prepared at ambient pressure. All of these compounds adopt the polar Ni3TeO6-type structure and order ferrimagnetically below the Néel temperature of 60 K. Meta-magnetic transitions are observed for x = 0.5 and 1 revealing complex magnetic behaviour. Ni2ScSbO6 is reported to have a helimagnetic spin order with propagation vector k = [0 0.036 0]. A remarkable series of long-period lock-in [0 0 1/3n] helical spin structures with n = 5, 6, 8 and 10 is found in Ni2-xCoxScSbO6, coexisting with a ferrimagnetic [0 0 0] phase at high Co-contents. The presence of electrical polarisation and spontaneous magnetisation offers possibilities for multiferroic properties.Ruthenium-containing metal oxides have a diverse range of unusual physical properties as a result of electron-electron correlations within broad 4d bands. A new perovskite material YRuO3 with non-magnetic Y3+ at the A-site, that is structurally similar to the LnRuO3 perovskites, has been synthesised at 1473 K and 15 GPa, and adopts a Pnma superstructure with a = 5.835(1), b = 7.528(1) and c = 5.193(1) Å. DC and AC magnetisation data both confirm that magnetic ordering occurs at around 97 K. Apparent changes in spin or domain relaxation processes are observed at 47.2 and 47.4 K in AC magnetisation data as well. Magnetisation steps evidence an unprecedented fractional weak ferromagnetic state at ¾ which reflects extreme single-ion anisotropy resulting from the strong spin-orbit coupling of the d5 Ru3+ ion. Resistivity measurements on a ceramic pellet display a semiconducting behaviour with a relatively small activation energy of 70 meV. A neutron diffraction study of YRuO3 reveals a G-type antiferromagnetic spin structure with an ordered moment of 0.33(3) µB at 1.7 K. The refined Ru-site is fully occupied, in comparison to the ~ 10 % Ru-site deficiency found in all the other LnRuO3 compounds, suggesting the existence of the pure unusual Ru3+ oxidation state. This study elucidates the electronic and magnetic properties of YRuO3, which appears to be the first Ru3+ oxide to exhibit spin ordering phenomena.en
dc.contributor.sponsorEngineering and Physical Sciences Research Council (EPSRC)en
dc.language.isoenen
dc.publisherThe University of Edinburghen
dc.relation.hasversionLock-in spin structures and ferrimagnetism in polar Ni2-xCoxScSbO6 oxides K. Ji, E. Solana-Madruga, A. M. Arevalo-Lopez, P. Manuel, C. Ritter, A. Senyshyne and J. Paul Attfield, Chem. Commun., 2018, 54, 12523en
dc.subjectcationcation interactionsen
dc.subjecttransition metal oxideen
dc.subjectmagnetic propertiesen
dc.subjectperovskiteen
dc.subjectcorundumen
dc.subjectstructural transitionsen
dc.titleSynthesis, structural and magnetic properties of some transition metal oxidesen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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