Phase Stability and Structural Evolution of Core/Shell Iron Oxide Nanoparticles Due to Oxidative Diffusion: Implications for Spintronic Applications

Nuñez, Jorge M.; Zysler, Roberto D.; Vásquez Mansilla, Marcelo; Bartolomé, Fernando; Winkler, Elin L.; Lohr, Javier Hernán; Aguirre, Myriam Haydee; Tolley, Alfredo; Lima, Enio; Rubín, Javier; Hettler, Simón; Arenal, Raúl

doi:10.1021/acsanm.5c01929

000162188 001__ 162188
000162188 005__ 20251204145007.0
000162188 0247_ $$2doi$$a10.1021/acsanm.5c01929
000162188 0248_ $$2sideral$$a144781
000162188 037__ $$aART-2025-144781
000162188 041__ $$aeng
000162188 100__ $$aNuñez, Jorge M.
000162188 245__ $$aPhase Stability and Structural Evolution of Core/Shell Iron Oxide Nanoparticles Due to Oxidative Diffusion: Implications for Spintronic Applications
000162188 260__ $$c2025
000162188 5203_ $$aCore/shell iron oxide nanoparticles are promising candidates for spintronic applications due to their tunable magnetic properties and interfacial exchange interactions that allow the modulation of spin-polarized conduction. However, their performance depends critically on phase stability and structural integrity under fabrication and operating conditions involving thermal and oxidative diffusion. This study examines the transformation of iron oxide nanoparticles induced by oxidative diffusion in thermal annealing from wüstite to hematite through an intermediate (wüstite)-core/(magnetite–maghemite)-shell structure. The nanoparticles exhibit a rounded cubic morphology, with a distorted C2/m FeO phase at the core under compressive strain along (010), while the Fe3O4 shell exhibits tensile strain along (110). Oxygen diffusion occurs preferentially along [100] from the cube faces, influencing shape evolution. The system exhibits an exchange bias field of up to 3 kOe and enhanced magnetic hardening of up to 4 kOe, attributed to interfacial exchange interactions. Higher annealing temperature promotes the formation of γ-Fe2O3 with ordered vacancies. The exchange bias effect persists, even when the FeO core is smaller than 1 nm in size, indicating that the strain stabilizes the antiferromagnetic (AFM) order and enhances core/shell magnetic coupling. As oxidation proceeds, strain is gradually relaxed, and at 873 K, the oxidation to hematite is promoted, characterized by a Morin transition at 245 K. These findings reveal the intricate relationship between oxidation-driven structural evolution and magnetic behavior in engineered nanoparticle systems, underscoring the critical importance of material selection tailored to specific fabrication processes, operating conditions, and device performance requirements.
000162188 536__ $$9info:eu-repo/grantAgreement/ES/DGA/E13-23R$$9info:eu-repo/grantAgreement/EC/H2020/101007629 /EU/Nanomaterials for Enzymatic Control of Oxidative Stress Toxicity and Free Radical Generation/NESTOR$$9This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 101007629 -NESTOR$$9info:eu-repo/grantAgreement/EC/H2020/101007825/EU/ULtra ThIn MAgneto Thermal sEnsor-Ing/ULTIMATE-I$$9This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 101007825-ULTIMATE-I$$9info:eu-repo/grantAgreement/EC/H2020/872631 /EU/Memristive and multiferroic materials for emergent logic units in nanoelectronics/MELON$$9This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 872631 -MELON$$9info:eu-repo/grantAgreement/ES/MICIU/CEX2023-001286-S$$9info:eu-repo/grantAgreement/ES/MICIU/PID2023-151080NB-I00
000162188 540__ $$9info:eu-repo/semantics/closedAccess$$aAll rights reserved$$uhttp://www.europeana.eu/rights/rr-f/
000162188 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion
000162188 700__ $$aLima, Enio
000162188 700__ $$aLohr, Javier Hernán
000162188 700__ $$aVásquez Mansilla, Marcelo
000162188 700__ $$aZysler, Roberto D.
000162188 700__ $$aTolley, Alfredo
000162188 700__ $$0(orcid)0000-0002-0047-1772$$aBartolomé, Fernando
000162188 700__ $$0(orcid)0000-0003-1029-3751$$aRubín, Javier$$uUniversidad de Zaragoza
000162188 700__ $$0(orcid)0000-0002-9102-7895$$aHettler, Simón
000162188 700__ $$0(orcid)0000-0002-2071-9093$$aArenal, Raúl
000162188 700__ $$0(orcid)0000-0002-1296-4793$$aAguirre, Myriam Haydee$$uUniversidad de Zaragoza
000162188 700__ $$aWinkler, Elin L.
000162188 7102_ $$15001$$2065$$aUniversidad de Zaragoza$$bDpto. Ciencia Tecnol.Mater.Fl.$$cÁrea Cienc.Mater. Ingen.Metal.
000162188 7102_ $$12003$$2395$$aUniversidad de Zaragoza$$bDpto. Física Materia Condensa.$$cÁrea Física Materia Condensada
000162188 773__ $$g8, 25 (2025), 13024-13036$$pACS appl. nano mater.$$tACS APPLIED NANO MATERIALS$$x2574-0970
000162188 8564_ $$s4615874$$uhttps://zaguan.unizar.es/record/162188/files/texto_completo.pdf$$yVersión publicada
000162188 8564_ $$s3204965$$uhttps://zaguan.unizar.es/record/162188/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada
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000162188 951__ $$a2025-12-04-14:45:24
000162188 980__ $$aARTICLE

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