TiO2 and ZnO metal oxides lattice defects driven magnetism and their contribution in discoloring of dyes
type: CreativeWork
description: We demonstrate that even wide band gap nonmagnetic materials as simple as ZnO and TiO2 with small concentrations of ionized oxygen vacancies and interstitial zinc or Ti can exhibit extraordinary properties. We show that the presence of oxygen vacancies turns the d10 nonmagnetic oxide into a ferromagnet. The study further shows an existence of a correlation between interstitial zinc on the magnetization hysteresis reversal. The observed reversal in hysteresis loop known as exchange coupling existing in a ferromagnet and antiferromagnet/ferrimagnet interface is currently observed only in similar morphological nanostructures. This remarkable observation suggests an existence of mixed and itinerate magnetism in one material. We have found a consistent correlation between the crystallite sizes and the shift in the exchange bias. Our ZnO hierarchical nanostructures are of “triangular- or samosas-like”, “platelets-like”, “hierarchical flowers-like” and “hexagonal open cups-like” structures possessing hexagonal internal structure of ZnO as demonstrated in our structural analysis. These ZnO nanostructures were synthesized in a shape-selective manner using simple microwave assisted hydrothermal synthesis. The direct correlation between the observed ferromagnetism and the relative concentration of oxygen and zinc vacancies that exist, suggest their vital role in modulating ferromagnetic behavior. These defects combination correspond to a g-factor value of > 2.1 depending on each structure. In addition, a novel low field microwave absorption signal was observed resulting from large surface areas due to nanostructuring. Moreover, there is an interesting and consistent twinning phenomena observed. The “samosas” tend to twins together with “hierarchical flowers” while “platelets” twin with “cups” nanostructures. Furthermore, we have synthesized ZnO nanorods. These nanorods seem to nucleate from one single rod and subsequently grow in numbers facing all different directions making …
abstract: We demonstrate that even wide band gap nonmagnetic materials as simple as ZnO and TiO2 with small concentrations of ionized oxygen vacancies and interstitial zinc or Ti can exhibit extraordinary properties. We show that the presence of oxygen vacancies turns the d10 nonmagnetic oxide into a ferromagnet. The study further shows an existence of a correlation between interstitial zinc on the magnetization hysteresis reversal. The observed reversal in hysteresis loop known as exchange coupling existing in a ferromagnet and antiferromagnet/ferrimagnet interface is currently observed only in similar morphological nanostructures. This remarkable observation suggests an existence of mixed and itinerate magnetism in one material. We have found a consistent correlation between the crystallite sizes and the shift in the exchange bias. Our ZnO hierarchical nanostructures are of “triangular- or samosas-like”, “platelets-like”, “hierarchical flowers-like” and “hexagonal open cups-like” structures possessing hexagonal internal structure of ZnO as demonstrated in our structural analysis. These ZnO nanostructures were synthesized in a shape-selective manner using simple microwave assisted hydrothermal synthesis. The direct correlation between the observed ferromagnetism and the relative concentration of oxygen and zinc vacancies that exist, suggest their vital role in modulating ferromagnetic behavior. These defects combination correspond to a g-factor value of > 2.1 depending on each structure. In addition, a novel low field microwave absorption signal was observed resulting from large surface areas due to nanostructuring. Moreover, there is an interesting and consistent twinning phenomena observed. The “samosas” tend to twins together with “hierarchical flowers” while “platelets” twin with “cups” nanostructures. Furthermore, we have synthesized ZnO nanorods. These nanorods seem to nucleate from one single rod and subsequently grow in numbers facing all different directions making …
author: Nkosi, Steven Solethu
keywords: zinc oxide(ZnO) --titanium dioxide(Ti02) --photo-catalytic activities --lattice defects --photoluminescence --ferromagnetism --electron spin resonance (ESR) --vibrating sample magnetometer (VSM) --X-Ray photoelectron spectroscopy
license: https://devspace.unizulu.ac.za/bitstreams/320fcc3e-2412-4a67-b717-d83ced60d51a/download
date published: 2017
date modified: 2026-07-24T06:16:58Z
provider: University of Zululand
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Zululand