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arXiv · 2410.00550

Exploring the complex interplay of anisotropies in magnetosomes of magnetotactic bacteria

David Gandia·Lourdes Marcano·Lucía Gandarias·Alicia G. Gubieda·Ana García-Prieto·Luis Fernández Barquín·Jose Ignacio Espeso·Elizabeth Martín Jefremovas·Iñaki Orue·Ana Abad Diaz de Cerio·M. Luisa Fdez-Gubieda·Javier Alonso
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Abstract

Magnetotactic bacteria (MTB) are of significant interest for biophysical applications, particularly in cancer treatment. The biomineralized magnetosomes produced by these bacteria are high-quality magnetic nanoparticles that form chains through a highly reproducible natural process. Specifically, Magnetovibrio blakemorei and Magnetospirillum gryphiswaldense exhibit distinct magnetosome morphologies: truncated hexa-octahedral and truncated octahedral shapes, respectively. Despite having identical compositions (magnetite, Fe3O4) and comparable dimensions, their effective uniaxial anisotropies differ significantly, with M. blakemorei showing ~25 kJ/m^3 and M. gryphiswaldense ~11 kJ/m^3 at 300K. This variation presents a unique opportunity to explore the role of different anisotropy contributions in the magnetic responses of magnetite-based nanoparticles. This study systematically investigates these responses by examining static magnetization as a function of temperature (M vs. T, 5 mT) and magnetic field (M vs. H, up to 1 T). Above the Verwey transition temperature (110 K), the effective anisotropy is dominated by shape anisotropy, notably increasing coercivity for M. blakemorei by up to two-fold compared to M. gryphiswaldense. Below this temperature, the effective uniaxial anisotropy increases non-monotonically, significantly altering magnetic behavior. Our simulations based on dynamic Stoner-Wohlfarth models indicate that below the Verwey temperature, a uniaxial magnetocrystalline contribution emerges, peaking at ~22-24 kJ/m^3 at 5 K, values close to those of bulk magnetite. This demonstrates the profound impact of anisotropic properties on the magnetic behaviors and applications of magnetite-based nanoparticles and highlights the exceptional utility of magnetosomes as ideal model systems for studying the complex interplay of anisotropies in magnetite-based nanoparticles.

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David Gandia, Lourdes Marcano, Lucía Gandarias, Alicia G. Gubieda, Ana García-Prieto, Luis Fernández Barquín, Jose Ignacio Espeso, Elizabeth Martín Jefremovas, Iñaki Orue, Ana Abad Diaz de Cerio, M. Luisa Fdez-Gubieda, Javier Alonso. 2024-10-01. Exploring the complex interplay of anisotropies in magnetosomes of magnetotactic bacteria. https://arxiv.org/abs/2410.00550

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