000163721 001__ 163721 000163721 005__ 20251030150827.0 000163721 0247_ $$2doi$$a10.1039/d5nh00254k 000163721 0248_ $$2sideral$$a145796 000163721 037__ $$aART-2025-145796 000163721 041__ $$aeng 000163721 100__ $$aOdio, Oscar F. 000163721 245__ $$aUnraveling the Mn<sup>2+</sup> substitution effect on the anisotropy control and magnetic hyperthermia of Mn<sub><i>x</i></sub>Fe<sub>3−<i>x</i></sub>O<sub>4</sub> nanoparticles 000163721 260__ $$c2025 000163721 5060_ $$aAccess copy available to the general public$$fUnrestricted 000163721 5203_ $$aComposition is a key parameter to effectively tune the magnetic anisotropy of magnetic nanoparticles, which in turn can modulate their structural–magnetic properties and final applications. The Mn2+ content of manganese ferrite nanoparticles (MnxFe3−xO4) deeply impacts their structure, anisotropy, magnetism, and their heating capacity. However, a direct correlation between Mn2+ content, magnetic properties and heating efficiency is not yet clear. Herein, we report the synthesis of a wide range of MnxFe3−xO4 with x = 0.14 to 1.40, with similar polyhedral morphologies and sizes (13 to 15 nm). By varying the Mn2+ content (in the range of x = 0.0 up to 0.70), we successfully tuned the effective anisotropy while maintaining saturation magnetization nearly constant. Highest Mn2+ levels (x = 1.40) lead to structural changes and strain defects reflected in their poor saturation magnetization. Mn2+ substitution is not uniform, instead promotes a compositional gradient across the MNPs, with the surface layers having a higher concentration of Mn2+ than the core. The Mn2+-rich surface likely exhibits superparamagnetic (SPM) relaxation, while the core remains predominantly ferrimagnetic (FiM). Water transference results in cation leaching, promoting vacancies and changes in the local ferrite structure but with a minor impact on the magnetic properties compared with initial MNPs. We obtained the optimal Mn2+ content that maximizes anisotropy toward improved specific loss power (SLP) values. The Néel relaxation mechanism is warranted regarding variable composition when sizes and shapes are maintained. Our detailed analysis provides a better understanding of the effect of Mn2+ substitution on the heating efficiency through anisotropy modulation and straightforward guidance on optimizing MNP design for magnetic hyperthermia. 000163721 536__ $$9info:eu-repo/grantAgreement/ES/DGA/E15-23R$$9info:eu-repo/grantAgreement/EC/H2020/853468/EU/Remote control of cellular signalling triggered by magnetic switching/SIROCCO$$9This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 853468-SIROCCO$$9info:eu-repo/grantAgreement/ES/MICINN-AEI/PRTR-C17.I1$$9info:eu-repo/grantAgreement/ES/MICINN/CNS2022-135700$$9info:eu-repo/grantAgreement/ES/MICINN/PID2021-122508NB-I00$$9info:eu-repo/grantAgreement/ES/MICIU/CEX2023-001286-S 000163721 540__ $$9info:eu-repo/semantics/openAccess$$aby$$uhttps://creativecommons.org/licenses/by/4.0/deed.es 000163721 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion 000163721 700__ $$aTommasini, Giuseppina 000163721 700__ $$aTeran, F. J. 000163721 700__ $$aOvejero, Jesus G. 000163721 700__ $$0(orcid)0000-0003-1029-3751$$aRubín, Javier$$uUniversidad de Zaragoza 000163721 700__ $$0(orcid)0000-0002-2861-2469$$aMoros, María 000163721 700__ $$aDel Sol-Fernández, Susel 000163721 7102_ $$15001$$2065$$aUniversidad de Zaragoza$$bDpto. Ciencia Tecnol.Mater.Fl.$$cÁrea Cienc.Mater. Ingen.Metal. 000163721 773__ $$g10, 10 (2025), 2486-2503$$pNanoscale Horizons$$tNanoscale Horizons$$x2055-6756 000163721 8564_ $$s7459971$$uhttps://zaguan.unizar.es/record/163721/files/texto_completo.pdf$$yVersión publicada 000163721 8564_ $$s3011077$$uhttps://zaguan.unizar.es/record/163721/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada 000163721 909CO $$ooai:zaguan.unizar.es:163721$$particulos$$pdriver 000163721 951__ $$a2025-10-30-14:39:41 000163721 980__ $$aARTICLE