{"id":{"repo_id":"gatech","oai_identifier":"oai:repository.gatech.edu:1853/77919"},"canonical_url":"https://search.dev.ndltd.org/etd/gatech/oai:repository.gatech.edu:1853/77919","repository":{"repo_id":"gatech","name":"Georgia Tech","base_url":"https://repository.gatech.edu/server/oai/request"},"display":{"title":"Chemical Correlation of Magnetic Permeability and Microwave Absorption in Spinel Ferrite Nanoparticles","abstract":"Spinel ferrites (MFe₂O₄, where M = Mn²⁺, Co²⁺, Zn²⁺, etc.) are magnetic nanomaterials with tunable properties that are valuable for wireless communication, memory storage, and electronics. Their complex permeabilities that are governed by composition, particle size, and spin-orbit interactions play a critical role in the determination of their electromagnetic performances. This dissertation explores the effect of chemical doping of nanoscale ferrites of 4 – 12 nm) on the complex permeability and ferromagnetic resonance (FMR) behavior. Size-dependent studies in MnFe₂O₄ and CoFe₂O₄ reveal that increasing particle size enhances both the real (μ′) and imaginary (μ″) parts of permeability due to reduced spin frustration and improved magnetic alignment. Doped CoxMn₁₋ₓFe₂O₄ ferrites show that increasing Co²⁺ lowers permeability, attributed to cobalt’s high magnetic anisotropy and spin-orbit coupling, while simultaneously minimizing its magnetic loss. In contrast, ZnxMn₁₋ₓFe₂O₄ and ZnxCo₁₋ₓFe₂O₄ exhibit rising μ′ and μ″ with increasing Zn²⁺ due to their associated reduced magnetic anisotropy and weakened exchange interactions. Ho³⁺ doping in MnFe₂O₄ leads to decreased permeability, as its large ionic radius and strong spin-orbit coupling disrupt exchange pathways. FMR analysis further highlights how magnetic anisotropy influences absorption. Co-rich ferrites display broader linewidths (FWHM), while Zn-rich variants show increased absorption from reduced damping. Interestingly, Co-containing ferrites demonstrated a unique FMR emission profile, likely resulting from cobalt's strong spin-orbit coupling and dynamic relaxation behavior. Rare-earth doped studies confirmed that such emission is specific to Co²⁺ environments and not solely due to spin-orbit strength. These results clarify how chemical composition modifications and nanoscale tuning governs the electromagnetic response of spinel ferrites, offering a library for high-performance magnetic materials in microwave technologies.","abstract_html":"Spinel ferrites (MFe₂O₄, where M = Mn²⁺, Co²⁺, Zn²⁺, etc.) are magnetic nanomaterials with tunable properties that are valuable for wireless communication, memory storage, and electronics. Their complex permeabilities that are governed by composition, particle size, and spin-orbit interactions play a critical role in the determination of their electromagnetic performances. This dissertation explores the effect of chemical doping of nanoscale ferrites of 4 – 12 nm) on the complex permeability and ferromagnetic resonance (FMR) behavior. Size-dependent studies in MnFe₂O₄ and CoFe₂O₄ reveal that increasing particle size enhances both the real (μ′) and imaginary (μ″) parts of permeability due to reduced spin frustration and improved magnetic alignment. Doped CoxMn₁₋ₓFe₂O₄ ferrites show that increasing Co²⁺ lowers permeability, attributed to cobalt’s high magnetic anisotropy and spin-orbit coupling, while simultaneously minimizing its magnetic loss. In contrast, ZnxMn₁₋ₓFe₂O₄ and ZnxCo₁₋ₓFe₂O₄ exhibit rising μ′ and μ″ with increasing Zn²⁺ due to their associated reduced magnetic anisotropy and weakened exchange interactions. Ho³⁺ doping in MnFe₂O₄ leads to decreased permeability, as its large ionic radius and strong spin-orbit coupling disrupt exchange pathways. FMR analysis further highlights how magnetic anisotropy influences absorption. Co-rich ferrites display broader linewidths (FWHM), while Zn-rich variants show increased absorption from reduced damping. Interestingly, Co-containing ferrites demonstrated a unique FMR emission profile, likely resulting from cobalt's strong spin-orbit coupling and dynamic relaxation behavior. Rare-earth doped studies confirmed that such emission is specific to Co²⁺ environments and not solely due to spin-orbit strength. These results clarify how chemical composition modifications and nanoscale tuning governs the electromagnetic response of spinel ferrites, offering a library for high-performance magnetic materials in microwave technologies.","abstract_has_math":false,"creators":["Aldama, Edgar"],"institution":"Georgia Institute of Technology","degree_name":null,"degree_level":"Doctoral","degree_discipline":null,"degree_department":"Chemistry and Biochemistry","school":null,"contributors":[],"advisors":["Zhang, Z. John"],"committee_chairs":[],"committee_members":["Wilkinson, Angus","La Pierre, Henry","Xia, Younan","Liu, Meilin"],"year":2025,"date_issued":"2025-04-28","date_published":"2025-04-28","updated_at":"2026-07-27T19:49:57Z","subjects":["Complex permeability","nanoparticles","spinel ferrites"],"languages":["en_US"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1853/77919","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Zhang, Z. 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Their complex permeabilities that are governed by composition, particle size, and spin-orbit interactions play a critical role in the determination of their electromagnetic performances. This dissertation explores the effect of chemical doping of nanoscale ferrites of 4 – 12 nm) on the complex permeability and ferromagnetic resonance (FMR) behavior. Size-dependent studies in MnFe₂O₄ and CoFe₂O₄ reveal that increasing particle size enhances both the real (μ′) and imaginary (μ″) parts of permeability due to reduced spin frustration and improved magnetic alignment. Doped CoxMn₁₋ₓFe₂O₄ ferrites show that increasing Co²⁺ lowers permeability, attributed to cobalt’s high magnetic anisotropy and spin-orbit coupling, while simultaneously minimizing its magnetic loss. In contrast, ZnxMn₁₋ₓFe₂O₄ and ZnxCo₁₋ₓFe₂O₄ exhibit rising μ′ and μ″ with increasing Zn²⁺ due to their associated reduced magnetic anisotropy and weakened exchange interactions. Ho³⁺ doping in MnFe₂O₄ leads to decreased permeability, as its large ionic radius and strong spin-orbit coupling disrupt exchange pathways. FMR analysis further highlights how magnetic anisotropy influences absorption. Co-rich ferrites display broader linewidths (FWHM), while Zn-rich variants show increased absorption from reduced damping. Interestingly, Co-containing ferrites demonstrated a unique FMR emission profile, likely resulting from cobalt's strong spin-orbit coupling and dynamic relaxation behavior. Rare-earth doped studies confirmed that such emission is specific to Co²⁺ environments and not solely due to spin-orbit strength. These results clarify how chemical composition modifications and nanoscale tuning governs the electromagnetic response of spinel ferrites, offering a library for high-performance magnetic materials in microwave technologies."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Chemical Correlation of Magnetic Permeability and Microwave Absorption in Spinel Ferrite Nanoparticles"]}]}],"canonical_facts":{"dc:contributor.advisor":["Zhang, Z. John"],"dc:contributor.committeemember":["Wilkinson, Angus","La Pierre, Henry","Xia, Younan","Liu, Meilin"],"dc:contributor.department":["Chemistry and Biochemistry"],"dc:creator":["Aldama, Edgar"],"dc:date.accessioned":["2025-06-23T15:27:11Z"],"dc:date.available":["2025-06-23T15:27:11Z"],"dc:date.issued":["2025-04-28"],"dc:description.abstract":["Spinel ferrites (MFe₂O₄, where M = Mn²⁺, Co²⁺, Zn²⁺, etc.) are magnetic nanomaterials with tunable properties that are valuable for wireless communication, memory storage, and electronics. Their complex permeabilities that are governed by composition, particle size, and spin-orbit interactions play a critical role in the determination of their electromagnetic performances. This dissertation explores the effect of chemical doping of nanoscale ferrites of 4 – 12 nm) on the complex permeability and ferromagnetic resonance (FMR) behavior. Size-dependent studies in MnFe₂O₄ and CoFe₂O₄ reveal that increasing particle size enhances both the real (μ′) and imaginary (μ″) parts of permeability due to reduced spin frustration and improved magnetic alignment. Doped CoxMn₁₋ₓFe₂O₄ ferrites show that increasing Co²⁺ lowers permeability, attributed to cobalt’s high magnetic anisotropy and spin-orbit coupling, while simultaneously minimizing its magnetic loss. In contrast, ZnxMn₁₋ₓFe₂O₄ and ZnxCo₁₋ₓFe₂O₄ exhibit rising μ′ and μ″ with increasing Zn²⁺ due to their associated reduced magnetic anisotropy and weakened exchange interactions. Ho³⁺ doping in MnFe₂O₄ leads to decreased permeability, as its large ionic radius and strong spin-orbit coupling disrupt exchange pathways. FMR analysis further highlights how magnetic anisotropy influences absorption. Co-rich ferrites display broader linewidths (FWHM), while Zn-rich variants show increased absorption from reduced damping. Interestingly, Co-containing ferrites demonstrated a unique FMR emission profile, likely resulting from cobalt's strong spin-orbit coupling and dynamic relaxation behavior. Rare-earth doped studies confirmed that such emission is specific to Co²⁺ environments and not solely due to spin-orbit strength. These results clarify how chemical composition modifications and nanoscale tuning governs the electromagnetic response of spinel ferrites, offering a library for high-performance magnetic materials in microwave technologies."],"dc:description.degree":["Ph.D."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["https://hdl.handle.net/1853/77919"],"dc:language.iso":["en_US"],"dc:publisher":["Georgia Institute of Technology"],"dc:subject":["Complex permeability","nanoparticles","spinel ferrites"],"dc:title":["Chemical Correlation of Magnetic Permeability and Microwave Absorption in Spinel Ferrite Nanoparticles"],"dc:type":["Text"],"thesis:degree_level":["Doctoral"]},"updated_at":"2026-07-27T19:49:57Z"}