{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/25274"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/25274","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Experimental study of the spin-glass phase diagram","abstract":"The spin-glass phase diagram is examined as a function of temperature, magnetic field, random anisotropy, and uniaxial anisotropy and the results are compared to recent mean-field theories. It is clearly demonstrated through measurements of the magnetic relaxation processes in the amorphous spin-glass (FeO.64MnO.36)75P16B6A13 that the onset of strong magnetic irreversibilities occurs at a field dependent temperature. The observed behavior agrees with the de Almeida-Thouless instability line predicted by mean-field theory. This line does not represent a phase transition, but instead marks a crossover from short to long relaxation times in the spin-glass phase. The presence of weak random anisotropy in CuMn4 at. % is found to make the spin-glass order parameter accessible through a measurement of the transverse ac susceptibility. The order parameter obeys thermodynamic scaling relations which show that the spin-glass transition occurs along the Gabay-Toulouse line, as expected from mean-field theory. The scaling of the transverse susceptibility data is strong evidence that the spin-glass phase is a true phase transition. In the moderately anisotropic spin-glass CuMn4 at. %Au1 at. % the anisotropic interactions distort the transition line. In small fields the anisotropy dominates, making the system behave in an Ising-like manner. At large fields, however, the anisotropy is overwhelmed and the system behaves as a Heisenberg spin-glass. This behavior agrees with recent mean-field results for anisotropic spin-glasses. The transition in the XY spin-glass YTb3 at. % is thoroughly examined using neutron diffraction, equilibrium susceptibility, non-linear susceptibility, and magnetic relaxation. This system exhibits typical spin-glass behavior, including: absence of long-range magnetic order, unidirectional an1sotropy, pseudo-logarithmic decay of the remanent magnetization, and scaling of the non-linear susceptibility. The spin-glass transition is clearly shown to occur only in the basal plane of this hexagonal system. The results of this work show that mean-field theory is a useful tool in examining real spin-glasses.","abstract_html":"The spin-glass phase diagram is examined as a function of temperature, magnetic field, random anisotropy, and uniaxial anisotropy and the results are compared to recent mean-field theories. It is clearly demonstrated through measurements of the magnetic relaxation processes in the amorphous spin-glass (FeO.64MnO.36)75P16B6A13 that the onset of strong magnetic irreversibilities occurs at a field dependent temperature. The observed behavior agrees with the de Almeida-Thouless instability line predicted by mean-field theory. This line does not represent a phase transition, but instead marks a crossover from short to long relaxation times in the spin-glass phase. The presence of weak random anisotropy in CuMn4 at. % is found to make the spin-glass order parameter accessible through a measurement of the transverse ac susceptibility. The order parameter obeys thermodynamic scaling relations which show that the spin-glass transition occurs along the Gabay-Toulouse line, as expected from mean-field theory. The scaling of the transverse susceptibility data is strong evidence that the spin-glass phase is a true phase transition. In the moderately anisotropic spin-glass CuMn4 at. %Au1 at. % the anisotropic interactions distort the transition line. In small fields the anisotropy dominates, making the system behave in an Ising-like manner. At large fields, however, the anisotropy is overwhelmed and the system behaves as a Heisenberg spin-glass. This behavior agrees with recent mean-field results for anisotropic spin-glasses. The transition in the XY spin-glass YTb3 at. % is thoroughly examined using neutron diffraction, equilibrium susceptibility, non-linear susceptibility, and magnetic relaxation. This system exhibits typical spin-glass behavior, including: absence of long-range magnetic order, unidirectional an1sotropy, pseudo-logarithmic decay of the remanent magnetization, and scaling of the non-linear susceptibility. The spin-glass transition is clearly shown to occur only in the basal plane of this hexagonal system. The results of this work show that mean-field theory is a useful tool in examining real spin-glasses.","abstract_has_math":false,"creators":["Ketelsen, Leonard Jan-Peter"],"institution":null,"degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Salamon, Myron B."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-06-03T18:20:21Z","date_published":"2011-06-03T18:20:21Z","updated_at":"2026-07-22T22:25:24Z","subjects":["spin-glass phase diagram","mean-field theories","magnetic relaxation processes","Almeida-Thouless instability line","relaxation times"],"languages":["en"],"rights":["1985 Leonard Jan-Peter Ketelsen"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["864932"],"render_values":[{"text":"864932","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/25274","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Salamon, Myron B."]},{"key":"dc:creator","label":"Author","values":["Ketelsen, Leonard Jan-Peter"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-06-03T18:20:21Z","10000-01-01","1985"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation / Thesis","text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["spin-glass phase diagram","mean-field theories","magnetic relaxation processes","Almeida-Thouless instability line","relaxation times"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["1985 Leonard Jan-Peter Ketelsen"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["864932","http://hdl.handle.net/2142/25274"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The spin-glass phase diagram is examined as a function of temperature, magnetic field, random anisotropy, and uniaxial anisotropy and the results are compared to recent mean-field theories. It is clearly demonstrated through measurements of the magnetic relaxation processes in the amorphous spin-glass (FeO.64MnO.36)75P16B6A13 that the onset of strong magnetic irreversibilities occurs at a field dependent temperature. The observed behavior agrees with the de Almeida-Thouless instability line predicted by mean-field theory. This line does not represent a phase transition, but instead marks a crossover from short to long relaxation times in the spin-glass phase. The presence of weak random anisotropy in CuMn4 at. % is found to make the spin-glass order parameter accessible through a measurement of the transverse ac susceptibility. The order parameter obeys thermodynamic scaling relations which show that the spin-glass transition occurs along the Gabay-Toulouse line, as expected from mean-field theory. The scaling of the transverse susceptibility data is strong evidence that the spin-glass phase is a true phase transition. In the moderately anisotropic spin-glass CuMn4 at. %Au1 at. % the anisotropic interactions distort the transition line. In small fields the anisotropy dominates, making the system behave in an Ising-like manner. At large fields, however, the anisotropy is overwhelmed and the system behaves as a Heisenberg spin-glass. This behavior agrees with recent mean-field results for anisotropic spin-glasses. The transition in the XY spin-glass YTb3 at. % is thoroughly examined using neutron diffraction, equilibrium susceptibility, non-linear susceptibility, and magnetic relaxation. This system exhibits typical spin-glass behavior, including: absence of long-range magnetic order, unidirectional an1sotropy, pseudo-logarithmic decay of the remanent magnetization, and scaling of the non-linear susceptibility. The spin-glass transition is clearly shown to occur only in the basal plane of this hexagonal system. The results of this work show that mean-field theory is a useful tool in examining real spin-glasses.","Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-03T18:20:21Z No. of bitstreams: 1 1985_ketelsen.pdf: 5814106 bytes, checksum: 6d11e9ea28298e5cb6ad9c867329b9fb (MD5)","Made available in DSpace on 2011-06-03T18:20:21Z (GMT). No. of bitstreams: 1 1985_ketelsen.pdf: 5814106 bytes, checksum: 6d11e9ea28298e5cb6ad9c867329b9fb (MD5) Previous issue date: 1985","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-03T18:20:21Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:15:19-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis","Thesis","U of I Only"]},{"key":"dc:title","label":"Title","values":["Experimental study of the spin-glass phase diagram"]}]}],"canonical_facts":{"dc:contributor":["Salamon, Myron B."],"dc:creator":["Ketelsen, Leonard Jan-Peter"],"dc:date":["2011-06-03T18:20:21Z","10000-01-01","1985"],"dc:description":["The spin-glass phase diagram is examined as a function of temperature, magnetic field, random anisotropy, and uniaxial anisotropy and the results are compared to recent mean-field theories. It is clearly demonstrated through measurements of the magnetic relaxation processes in the amorphous spin-glass (FeO.64MnO.36)75P16B6A13 that the onset of strong magnetic irreversibilities occurs at a field dependent temperature. The observed behavior agrees with the de Almeida-Thouless instability line predicted by mean-field theory. This line does not represent a phase transition, but instead marks a crossover from short to long relaxation times in the spin-glass phase. The presence of weak random anisotropy in CuMn4 at. % is found to make the spin-glass order parameter accessible through a measurement of the transverse ac susceptibility. The order parameter obeys thermodynamic scaling relations which show that the spin-glass transition occurs along the Gabay-Toulouse line, as expected from mean-field theory. The scaling of the transverse susceptibility data is strong evidence that the spin-glass phase is a true phase transition. In the moderately anisotropic spin-glass CuMn4 at. %Au1 at. % the anisotropic interactions distort the transition line. In small fields the anisotropy dominates, making the system behave in an Ising-like manner. At large fields, however, the anisotropy is overwhelmed and the system behaves as a Heisenberg spin-glass. This behavior agrees with recent mean-field results for anisotropic spin-glasses. The transition in the XY spin-glass YTb3 at. % is thoroughly examined using neutron diffraction, equilibrium susceptibility, non-linear susceptibility, and magnetic relaxation. This system exhibits typical spin-glass behavior, including: absence of long-range magnetic order, unidirectional an1sotropy, pseudo-logarithmic decay of the remanent magnetization, and scaling of the non-linear susceptibility. The spin-glass transition is clearly shown to occur only in the basal plane of this hexagonal system. The results of this work show that mean-field theory is a useful tool in examining real spin-glasses.","Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-03T18:20:21Z No. of bitstreams: 1 1985_ketelsen.pdf: 5814106 bytes, checksum: 6d11e9ea28298e5cb6ad9c867329b9fb (MD5)","Made available in DSpace on 2011-06-03T18:20:21Z (GMT). No. of bitstreams: 1 1985_ketelsen.pdf: 5814106 bytes, checksum: 6d11e9ea28298e5cb6ad9c867329b9fb (MD5) Previous issue date: 1985","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-03T18:20:21Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:15:19-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis","Thesis","U of I Only"],"dc:identifier":["864932","http://hdl.handle.net/2142/25274"],"dc:language":["en"],"dc:rights":["1985 Leonard Jan-Peter Ketelsen"],"dc:subject":["spin-glass phase diagram","mean-field theories","magnetic relaxation processes","Almeida-Thouless instability line","relaxation times"],"dc:title":["Experimental study of the spin-glass phase diagram"],"dc:type":["Dissertation / Thesis","text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."]},"updated_at":"2026-07-22T22:25:24Z"}