{"id":{"repo_id":"ghent","oai_identifier":"oai:archive.ugent.be:811761"},"canonical_url":"https://search.dev.ndltd.org/etd/ghent/oai:archive.ugent.be:811761","repository":{"repo_id":"ghent","name":"Ghent University","base_url":"https://biblio.ugent.be/oai"},"display":{"title":"57Fe Mössbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4","abstract":"Magnetically diluted materials with spinel structure can fulfil the conditions for spin-glass behaviour. On the other hand, such spinels were also reported to exhibit a superparamagnetic behaviour due to the existence of small magnetic clusters in the spinel lattice. In order to gain some insight in this controversial problem, a 57Fe Mössbauer spectroscopic study has been performed on some new spinel compounds with general formula Mg+x-yFe2(1-x)NiyTixO4 with x=0.5, 0.6 and 0.7 and y being 0.1. The Ni2+ was introduced with the aim to resolve better the contributions of both spinel sublattices in the external-field Mössbauer spectra. In the first place, special attention has been paid to the preparation procedures. It has been found that as-prepared samples show a predominant superparamagnetic behaviour due to magnetic clusters within the sample. After repeating the heating process for at least three times the samples behave more as a spin glass. From the Mössbauer experiments it has been shown that for the composition with x=0.7 a direct transition from paramagnetism to spin glass occurs on cooling, whereas for the compositions with x=0.5 and 0.6 an intermediate ferrimagnetic phase is observed with a transversal spin relaxation on the octahedral sites. At lower temperatures these compositions freeze to a spin glass on the octahedral sites while the spins on the tetrahedral sites remain mutually parallel and opposite to the net B-site moment. Finally, from the experimental data combined with the percollation thresholds reported in literature, boundary values with respect to composition and temperature could be derived enabling to draw up a complete magnetic phase diagram.","abstract_html":"Magnetically diluted materials with spinel structure can fulfil the conditions for spin-glass behaviour. On the other hand, such spinels were also reported to exhibit a superparamagnetic behaviour due to the existence of small magnetic clusters in the spinel lattice. In order to gain some insight in this controversial problem, a 57Fe Mössbauer spectroscopic study has been performed on some new spinel compounds with general formula Mg+x-yFe2(1-x)NiyTixO4 with x=0.5, 0.6 and 0.7 and y being 0.1. The Ni2+ was introduced with the aim to resolve better the contributions of both spinel sublattices in the external-field Mössbauer spectra. In the first place, special attention has been paid to the preparation procedures. It has been found that as-prepared samples show a predominant superparamagnetic behaviour due to magnetic clusters within the sample. After repeating the heating process for at least three times the samples behave more as a spin glass. From the Mössbauer experiments it has been shown that for the composition with x=0.7 a direct transition from paramagnetism to spin glass occurs on cooling, whereas for the compositions with x=0.5 and 0.6 an intermediate ferrimagnetic phase is observed with a transversal spin relaxation on the octahedral sites. At lower temperatures these compositions freeze to a spin glass on the octahedral sites while the spins on the tetrahedral sites remain mutually parallel and opposite to the net B-site moment. Finally, from the experimental data combined with the percollation thresholds reported in literature, boundary values with respect to composition and temperature could be derived enabling to draw up a complete magnetic phase diagram.","abstract_has_math":false,"creators":["Alakrmi, Abdurazak"],"institution":"Ghent University. Faculty of Sciences","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["De Grave, Eddy","Vandenberghe, Robert"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2009,"date_issued":"2009","date_published":"2009","updated_at":"2026-07-24T02:22:55Z","subjects":["Physics and Astronomy"],"languages":["eng"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://biblio.ugent.be/publication/811761","https://biblio.ugent.be/publication/811761/file/1886381"],"render_values":[{"text":"https://biblio.ugent.be/publication/811761","href":"https://biblio.ugent.be/publication/811761","code":true},{"text":"https://biblio.ugent.be/publication/811761/file/1886381","href":"https://biblio.ugent.be/publication/811761/file/1886381","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/1854/LU-811761","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["De Grave, Eddy","Vandenberghe, Robert"]},{"key":"dc:creator","label":"Author","values":["Alakrmi, Abdurazak"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2009"]},{"key":"dc:publisher","label":"Institution","values":["Ghent University. Faculty of Sciences"]},{"key":"dc:type","label":"Dc Type","values":["dissertation","info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics and Astronomy"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://biblio.ugent.be/publication/811761","http://hdl.handle.net/1854/LU-811761","https://biblio.ugent.be/publication/811761/file/1886381"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Magnetically diluted materials with spinel structure can fulfil the conditions for spin-glass behaviour. On the other hand, such spinels were also reported to exhibit a superparamagnetic behaviour due to the existence of small magnetic clusters in the spinel lattice. In order to gain some insight in this controversial problem, a 57Fe Mössbauer spectroscopic study has been performed on some new spinel compounds with general formula Mg+x-yFe2(1-x)NiyTixO4 with x=0.5, 0.6 and 0.7 and y being 0.1. The Ni2+ was introduced with the aim to resolve better the contributions of both spinel sublattices in the external-field Mössbauer spectra. In the first place, special attention has been paid to the preparation procedures. It has been found that as-prepared samples show a predominant superparamagnetic behaviour due to magnetic clusters within the sample. After repeating the heating process for at least three times the samples behave more as a spin glass. From the Mössbauer experiments it has been shown that for the composition with x=0.7 a direct transition from paramagnetism to spin glass occurs on cooling, whereas for the compositions with x=0.5 and 0.6 an intermediate ferrimagnetic phase is observed with a transversal spin relaxation on the octahedral sites. At lower temperatures these compositions freeze to a spin glass on the octahedral sites while the spins on the tetrahedral sites remain mutually parallel and opposite to the net B-site moment. Finally, from the experimental data combined with the percollation thresholds reported in literature, boundary values with respect to composition and temperature could be derived enabling to draw up a complete magnetic phase diagram."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["57Fe Mössbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4"]}]}],"canonical_facts":{"dc:contributor":["De Grave, Eddy","Vandenberghe, Robert"],"dc:creator":["Alakrmi, Abdurazak"],"dc:date":["2009"],"dc:description":["Magnetically diluted materials with spinel structure can fulfil the conditions for spin-glass behaviour. On the other hand, such spinels were also reported to exhibit a superparamagnetic behaviour due to the existence of small magnetic clusters in the spinel lattice. In order to gain some insight in this controversial problem, a 57Fe Mössbauer spectroscopic study has been performed on some new spinel compounds with general formula Mg+x-yFe2(1-x)NiyTixO4 with x=0.5, 0.6 and 0.7 and y being 0.1. The Ni2+ was introduced with the aim to resolve better the contributions of both spinel sublattices in the external-field Mössbauer spectra. In the first place, special attention has been paid to the preparation procedures. It has been found that as-prepared samples show a predominant superparamagnetic behaviour due to magnetic clusters within the sample. After repeating the heating process for at least three times the samples behave more as a spin glass. From the Mössbauer experiments it has been shown that for the composition with x=0.7 a direct transition from paramagnetism to spin glass occurs on cooling, whereas for the compositions with x=0.5 and 0.6 an intermediate ferrimagnetic phase is observed with a transversal spin relaxation on the octahedral sites. At lower temperatures these compositions freeze to a spin glass on the octahedral sites while the spins on the tetrahedral sites remain mutually parallel and opposite to the net B-site moment. Finally, from the experimental data combined with the percollation thresholds reported in literature, boundary values with respect to composition and temperature could be derived enabling to draw up a complete magnetic phase diagram."],"dc:format":["application/pdf"],"dc:identifier":["https://biblio.ugent.be/publication/811761","http://hdl.handle.net/1854/LU-811761","https://biblio.ugent.be/publication/811761/file/1886381"],"dc:language":["eng"],"dc:publisher":["Ghent University. Faculty of Sciences"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:subject":["Physics and Astronomy"],"dc:title":["57Fe Mössbauer spectroscopic study of the spin-glass transitions in the mixed spinel series Mg0.9+xFe2(1-x)Ni0.1Ti0.1O4"],"dc:type":["dissertation","info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-24T02:22:55Z"}