Interplay of chemical doping, crystal structure and magnetism in oxygen non-stoichiometric Nd2-xSrxNiO4+δ

Diplôme Thèse Interplay of chemical doping, crystal structure and magnetism in oxygen non-stoichiometric Nd2-xSrxNiO4+δ eng 2020-01-17 author Maity Sumit Ranjan 853624 director Ruegg Christian 790594 director Keller Lukas 660238 10.13097/archive-ouverte/unige:131881 urn:nbn:ch:unige-1318817 Sc. 5432 The fundamental understanding of the microscopic origin of oxygen diffusion is essential to design and optimize new oxygen ion conductors for technological applications. In this work, using single crystal neutron diffraction studies on Sr and O-doped Nd2NiO4+δ compounds, we have shown strong anharmonic delocalization of apical oxygen atoms specifically towards the nearest oxygen interstitial sites which are related to specific low energy local structural distortions induced by the excess oxygens. These structural distortions are prerequisites to trigger oxygen mobility close to room temperature. The subsequent oxygen diffusion mechanism is closely related to the “phonon assisted diffusion mechanism” providing an atomistic description of non-classical oxygen diffusion process in non-stoichiometric oxides at low temperature. A commensurate antiferromagnetic spin order is observed in Nd2NiO4.1 in contrast to an incommensurate magnetic order in Nd2NiO4.23. The observed incommensurate magnetic phase is different from the usual stripe type magnetic order observed in isoelectronic Sr-doped Nd1.5Sr0.5NiO4+δ compound. Dewey 500.2 33 Département de physique de la matière quantique 131 false 9b7d0bd5-c28f-4078-84b3-ba648964e357 Thesis Public Thesis_Maity.pdf 15495102 application/pdf Private 2020-09-09 c87b36d3eb6ad156cdcafdd6a3246e5affb23f5964ad3578b9a17f30d9aa064b openAccess Faculté des sciences / Section de physique / Département de physique de la matière quantique

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Interplay of chemical doping, crystal structure and magnetism in oxygen non-stoichiometric Nd2-xSrxNiO4+δ				2020	900	746

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Maity, Sumit Ranjan