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arXiv · 2005.07947

Vacancy-driven non-cubic local structure and magnetic anisotropy tailoring in Fe$_x$O-Fe$_{3-\delta}$O$_4$ nanocrystals

Alexandros Lappas·George Antonaropoulos·Konstantinos Brintakis·Marianna Vasilakaki·Kalliopi N. Trohidou·Vincenzo Iannotti·Giovanni Ausanio·Athanasia Kostopoulou·Milinda Abeykoon·Ian K. Robinson·Emil S. Bozin
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Abstract

In contrast to bulk materials, nanoscale crystal growth is critically influenced by size- and shape-dependent properties. However, it is challenging to decipher how stoichiometry, in the realm of mixed-valence elements, can act to control physical properties, especially when complex bonding is implicated by short and long-range ordering of structural defects. Here, solution-grown iron-oxide nanocrystals (NCs) of the pilot wustite system are found to convert into iron-deficient rock-salt and ferro-spinel sub-domains, but attain a surprising tetragonally distorted local structure. Cationic vacancies within chemically uniform NCs are portrayed as the parameter to tweak the underlying properties. These lattice imperfections are shown to produce local exchange-anisotropy fields that reinforce the nanoparticles magnetization and overcome the influence of finite-size effects. The concept of atomic-scale defect control in subcritical size NCs, aspires to become a pathway to tailor-made properties with improved performance for hyperthermia heating over defect-free NCs.

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Alexandros Lappas, George Antonaropoulos, Konstantinos Brintakis, Marianna Vasilakaki, Kalliopi N. Trohidou, Vincenzo Iannotti, Giovanni Ausanio, Athanasia Kostopoulou, Milinda Abeykoon, Ian K. Robinson, Emil S. Bozin. 2020-05-16. Vacancy-driven non-cubic local structure and magnetic anisotropy tailoring in Fe$_x$O-Fe$_{3-\delta}$O$_4$ nanocrystals. https://doi.org/10.1103/physrevx.9.041044

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