arXiv subjects

Iñaki Orue

Publications and source records attributed to Iñaki Orue.

3 recordsLinked to original sources

arXiv2025

Strain Engineering of Magnetoresistance and Magnetic Anisotropy in CrSBr

Tailoring magnetoresistance and magnetic anisotropy in van der Waals magnetic materials is essential for advancing their integration into technological applications. In this regard, strain engineering has emerged as a powerful and versatile strategy to control magnetism at the two-dimensional (2D) limit. Here, we demonstrate that compressive biaxial strain significantly enhances the magnetoresistance and magnetic anisotropy of few-layer CrSBr flakes. Strain is efficiently transferred to the flakes from the thermal compression of a polymeric substrate upon cooling, as confirmed by temperature-dependent Raman spectroscopy. This strain induces a remarkable increase in the magnetoresistance ratio and in the saturation fields required to align the magnetization of CrSBr along each of its three crystalographic directions, reaching a twofold enhancement along the magnetic easy axis. This enhancement is accompanied by a subtle reduction of the Néel temperature by ~10K. Our experimental results are fully supported by first-principles calculations, which link the observed effects to a strain-driven modification in interlayer exchange coupling and magnetic anisotropy energy. These findings establish strain engineering as a key tool for fine-tuning magnetotransport properties in 2D magnetic semiconductors, paving the way for implementation in spintronics and information storage devices.

cond-mat.mtrl-sci↗

arXiv2024

Exploring the complex interplay of anisotropies in magnetosomes of magnetotactic bacteria

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.

cond-mat.mtrl-sci↗

arXiv2020

Probing the stability and magnetic properties of magnetosome chains in freeze-dried magnetotactic bacteria

\textit{Magnetospirillum gryphiswaldense} biosynthesize high quality magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Here we perform magnetometry and polarized small-angle neutron scattering (SANS) experiments on a powder of freeze-dried and immobilized \textit{M. gryphiswaldense}. We confirm that the individual nanoparticles are single-domain particles and that an alignment of the particle moments in field direction occurs exclusively by a Néel-like rotation. Our magnetometry results of the bacteria powder indicate an absence of dipolar interactions between the particle chains and a dominant uniaxial magnetic anisotropy. Finally, we can verify by SANS that the chain structure within the immobilized, freeze-dried bacteria is preserved also after application of large magnetic fields of up to 1\,T.

cond-mat.soft↗