{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/42638"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/42638","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Induced Phase Transition in Magnetoelectric BiFeO3 Crystals, Thin-layers and Ceramics","abstract":"Bismuth ferrite (BiFeO₃) is a magneto-electric material which exhibits simultaneously ferroelectric and antiferromagnetic properties. We have used high-field electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic range of 0-25 Tesla. With increasing magnetic field, an induced transition has been found between incommensurately modulated cycloidal antiferromagnetic and homogeneous magnetized spin state. The data reveal a number of interesting changes with increasing field, including: (i) significant changes in the ESR spectra; (ii) hysteresis in the spectra near the critical field. We have analyzed the changes in the ESR spectra by taking into account the magnetic anisotropy of the crystal and the homogeneous anti-symmetric Dzyaloshinsky-Moria exchange. We have also investigated phase induced transition by epitaxial constraint, and substituent and cystalline solution effects. Variously oriented BiFeO₃ epitaxial thin films have been deposited by pulsed laser deposition. Dramatically enhanced polarization has been found for (001)c, (110)c, and (111)c films, relative to that of BiFeO₃ crystals. The easy axis of spontaneous polarization lies close to (111)c for the variously oriented films. BiFeO₃ films grown on (111)c have a rhombohedral structure, identical to that of single crystals. Whereas, films grown on (110)c or (001)c are explained in terms of an epitaxially-induced transition between cycloidal and homogeneous spin states, via magneto-electric interactions. Finally, lanthanum modified BiFeO₃-xPbTiO₃ crystalline solutions have been found to have a large linear magneto-electric coefficient, ∝p. The value of ∝p (2.5x10⁻⁹ s/m or C/m²-Oe) is ∼10x greater than that of any other material (cg., Cr₂O₃ ∼2.5x10⁻¹⁰ s/m), and many order(s) of magnitude higher than unmodified BiFeO₃ crystals. The data also reveal: (i) that ∝p is due to a linear coupling between polarization and magnetization; and (ii) that ∝p is independent of dc magnetic bias and ac magnetic field. We show that the ME effect is significantly enhanced due to the breaking of the transitional invariance of a long-period spiral spin structure, via randomly distributed charged imperfections.","abstract_html":"Bismuth ferrite (BiFeO₃) is a magneto-electric material which exhibits simultaneously ferroelectric and antiferromagnetic properties. We have used high-field electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic range of 0-25 Tesla. With increasing magnetic field, an induced transition has been found between incommensurately modulated cycloidal antiferromagnetic and homogeneous magnetized spin state. The data reveal a number of interesting changes with increasing field, including: (i) significant changes in the ESR spectra; (ii) hysteresis in the spectra near the critical field. We have analyzed the changes in the ESR spectra by taking into account the magnetic anisotropy of the crystal and the homogeneous anti-symmetric Dzyaloshinsky-Moria exchange. We have also investigated phase induced transition by epitaxial constraint, and substituent and cystalline solution effects. Variously oriented BiFeO₃ epitaxial thin films have been deposited by pulsed laser deposition. Dramatically enhanced polarization has been found for (001)c, (110)c, and (111)c films, relative to that of BiFeO₃ crystals. The easy axis of spontaneous polarization lies close to (111)c for the variously oriented films. BiFeO₃ films grown on (111)c have a rhombohedral structure, identical to that of single crystals. Whereas, films grown on (110)c or (001)c are explained in terms of an epitaxially-induced transition between cycloidal and homogeneous spin states, via magneto-electric interactions. Finally, lanthanum modified BiFeO₃-xPbTiO₃ crystalline solutions have been found to have a large linear magneto-electric coefficient, ∝p. The value of ∝p (2.5x10⁻⁹ s/m or C/m²-Oe) is ∼10x greater than that of any other material (cg., Cr₂O₃ ∼2.5x10⁻¹⁰ s/m), and many order(s) of magnitude higher than unmodified BiFeO₃ crystals. The data also reveal: (i) that ∝p is due to a linear coupling between polarization and magnetization; and (ii) that ∝p is independent of dc magnetic bias and ac magnetic field. We show that the ME effect is significantly enhanced due to the breaking of the transitional invariance of a long-period spiral spin structure, via randomly distributed charged imperfections.","abstract_has_math":false,"creators":["Ruette, Benjamin Thibault"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Materials Science and Engineering","degree_department":"Materials Science and Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Viehland, Dwight D."],"committee_members":["Li, Jie-Fang","Claus, Richard O."],"year":2003,"date_issued":"2003-05-22","date_published":"2003-05-22","updated_at":"2026-07-22T22:20:23Z","subjects":["Ferrite","Bismuth","Perovskite","Magnetoelectric","Crystals"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-05122003-102123"],"render_values":[{"text":"etd-05122003-102123","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/42638","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Viehland, Dwight D."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Li, Jie-Fang","Claus, Richard O."]},{"key":"dc:contributor.department","label":"Department","values":["Materials Science and Engineering"]},{"key":"dc:creator","label":"Author","values":["Ruette, Benjamin Thibault"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T21:36:08Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T21:36:08Z","2004-09-09"]},{"key":"dc:date.issued","label":"Date","values":["2003-05-22"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science and Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Ferrite","Bismuth","Perovskite","Magnetoelectric","Crystals"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-05122003-102123"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/42638"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Bismuth ferrite (BiFeO₃) is a magneto-electric material which exhibits simultaneously ferroelectric and antiferromagnetic properties. We have used high-field electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic range of 0-25 Tesla. With increasing magnetic field, an induced transition has been found between incommensurately modulated cycloidal antiferromagnetic and homogeneous magnetized spin state. The data reveal a number of interesting changes with increasing field, including: (i) significant changes in the ESR spectra; (ii) hysteresis in the spectra near the critical field. We have analyzed the changes in the ESR spectra by taking into account the magnetic anisotropy of the crystal and the homogeneous anti-symmetric Dzyaloshinsky-Moria exchange. We have also investigated phase induced transition by epitaxial constraint, and substituent and cystalline solution effects. Variously oriented BiFeO₃ epitaxial thin films have been deposited by pulsed laser deposition. Dramatically enhanced polarization has been found for (001)c, (110)c, and (111)c films, relative to that of BiFeO₃ crystals. The easy axis of spontaneous polarization lies close to (111)c for the variously oriented films. BiFeO₃ films grown on (111)c have a rhombohedral structure, identical to that of single crystals. Whereas, films grown on (110)c or (001)c are explained in terms of an epitaxially-induced transition between cycloidal and homogeneous spin states, via magneto-electric interactions. Finally, lanthanum modified BiFeO₃-xPbTiO₃ crystalline solutions have been found to have a large linear magneto-electric coefficient, ∝p. The value of ∝p (2.5x10⁻⁹ s/m or C/m²-Oe) is ∼10x greater than that of any other material (cg., Cr₂O₃ ∼2.5x10⁻¹⁰ s/m), and many order(s) of magnitude higher than unmodified BiFeO₃ crystals. The data also reveal: (i) that ∝p is due to a linear coupling between polarization and magnetization; and (ii) that ∝p is independent of dc magnetic bias and ac magnetic field. We show that the ME effect is significantly enhanced due to the breaking of the transitional invariance of a long-period spiral spin structure, via randomly distributed charged imperfections."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["Induced Phase Transition in Magnetoelectric BiFeO3 Crystals, Thin-layers and Ceramics"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Viehland, Dwight D."],"dc:contributor.committeemember":["Li, Jie-Fang","Claus, Richard O."],"dc:contributor.department":["Materials Science and Engineering"],"dc:creator":["Ruette, Benjamin Thibault"],"dc:date.accessioned":["2014-03-14T21:36:08Z"],"dc:date.available":["2014-03-14T21:36:08Z","2004-09-09"],"dc:date.issued":["2003-05-22"],"dc:description.abstract":["Bismuth ferrite (BiFeO₃) is a magneto-electric material which exhibits simultaneously ferroelectric and antiferromagnetic properties. We have used high-field electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic range of 0-25 Tesla. With increasing magnetic field, an induced transition has been found between incommensurately modulated cycloidal antiferromagnetic and homogeneous magnetized spin state. The data reveal a number of interesting changes with increasing field, including: (i) significant changes in the ESR spectra; (ii) hysteresis in the spectra near the critical field. We have analyzed the changes in the ESR spectra by taking into account the magnetic anisotropy of the crystal and the homogeneous anti-symmetric Dzyaloshinsky-Moria exchange. We have also investigated phase induced transition by epitaxial constraint, and substituent and cystalline solution effects. Variously oriented BiFeO₃ epitaxial thin films have been deposited by pulsed laser deposition. Dramatically enhanced polarization has been found for (001)c, (110)c, and (111)c films, relative to that of BiFeO₃ crystals. The easy axis of spontaneous polarization lies close to (111)c for the variously oriented films. BiFeO₃ films grown on (111)c have a rhombohedral structure, identical to that of single crystals. Whereas, films grown on (110)c or (001)c are explained in terms of an epitaxially-induced transition between cycloidal and homogeneous spin states, via magneto-electric interactions. Finally, lanthanum modified BiFeO₃-xPbTiO₃ crystalline solutions have been found to have a large linear magneto-electric coefficient, ∝p. The value of ∝p (2.5x10⁻⁹ s/m or C/m²-Oe) is ∼10x greater than that of any other material (cg., Cr₂O₃ ∼2.5x10⁻¹⁰ s/m), and many order(s) of magnitude higher than unmodified BiFeO₃ crystals. The data also reveal: (i) that ∝p is due to a linear coupling between polarization and magnetization; and (ii) that ∝p is independent of dc magnetic bias and ac magnetic field. We show that the ME effect is significantly enhanced due to the breaking of the transitional invariance of a long-period spiral spin structure, via randomly distributed charged imperfections."],"dc:description.degree":["Master of Science"],"dc:identifier.other":["etd-05122003-102123"],"dc:identifier.uri":["http://hdl.handle.net/10919/42638"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Ferrite","Bismuth","Perovskite","Magnetoelectric","Crystals"],"dc:title":["Induced Phase Transition in Magnetoelectric BiFeO3 Crystals, Thin-layers and Ceramics"],"dc:type":["Thesis"],"thesis:degree_discipline":["Materials Science and Engineering"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:23Z"}