Engineering hard ferrite composites by combining nanostructuring and Al3+ Substitution: From nano to dense bulk magnets

IF 8.3 1区材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY

Acta Materialia Pub Date : 2024-10-18 DOI:10.1016/j.actamat.2024.120491

Pierfrancesco Maltoni , Gianni Barucca , Bogdan Rutkowski , Sergey A. Ivanov , Nader Yaacoub , Anastasiia Mikheenkova , Gustav Ek , Mirva Eriksson , Bjarne Almqvist , Marianna Vasilakaki , Gaspare Varvaro , Tapati Sarkar , José A. De Toro , Kalliopi Trohidou , Davide Peddis , Roland Mathieu

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Abstract

We have investigated the bottom-up sol-gel synthesis of nanocomposite powders comprising two magnetic phases (hexagonal Sr ferrite and spinel Co ferrite) in order to outline a strategy to obtain permanent magnets with large coercivities via low-cost and scalable syntheses. The correlation between morphological, structural and macroscopic magnetic properties of Al-substituted SrFe₁₂O₁₉ and SrFe₁₂O₁₉/CoFe₂O₄ nanocomposites was analyzed in detail. The hysteretic behavior can be tuned by cation substitution and/or modulation of the super-exchange coupling at the interface of the constituting phases. The magnetic data, supported by Monte Carlo simulations, indicates enhanced magnetic coupling within the composite: this observation underscores the significance of soft crystallite size and epitaxial growth quality at the interface as key factors influencing super-exchange coupling strength, ranging from fully coupled to essentially decoupled composites. Bulk magnets with high density were manufactured by compacting these nanostructured phases using spark plasma sintering, without an applied magnetic field. Consolidation of powders significantly impacted magnetic properties, by increasing remanent magnetization and decreasing coercivity due to enhanced super-exchange coupling. The presence of two phases hindered reciprocal growth, influencing coercivity differently in various compositions. Overall, the compaction enhanced magnet performance through improved particle alignment and super-exchange coupling, offering the potential for optimized magnet design.

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结合纳米结构和 Al3+ 替代技术，制造硬质铁氧体复合材料：从纳米到致密块状磁体

我们研究了由两种磁性相（六方态 Sr 铁氧体和尖晶石态 Co 铁氧体）组成的纳米复合粉末的自下而上溶胶-凝胶合成，从而勾勒出一种通过低成本和可扩展合成获得大矫顽力永磁体的策略。详细分析了铝取代的 SrFe12O19 和 SrFe12O19/CoFe2O4 纳米复合材料的形态、结构和宏观磁性能之间的相关性。滞后行为可通过阳离子替代和/或构成相界面上的超交换耦合调节。蒙特卡洛模拟支持的磁性数据表明，复合材料内部的磁耦合增强了：这一观察结果强调了界面处软晶体尺寸和外延生长质量的重要性，它们是影响超交换耦合强度的关键因素。在没有外加磁场的情况下，利用火花等离子烧结压实这些纳米结构相，制造出了高密度的块状磁体。由于超交换耦合增强，粉末的固结会增加剩磁，降低矫顽力，从而对磁性能产生重大影响。两相的存在阻碍了互生，对不同成分的矫顽力产生了不同的影响。总之，压实通过改善颗粒排列和超交换耦合提高了磁体性能，为优化磁体设计提供了可能。

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来源期刊

Acta Materialia 工程技术-材料科学：综合

CiteScore

16.10

自引率

8.50%

发文量

801

审稿时长

53 days

期刊介绍： Acta Materialia serves as a platform for publishing full-length, original papers and commissioned overviews that contribute to a profound understanding of the correlation between the processing, structure, and properties of inorganic materials. The journal seeks papers with high impact potential or those that significantly propel the field forward. The scope includes the atomic and molecular arrangements, chemical and electronic structures, and microstructure of materials, focusing on their mechanical or functional behavior across all length scales, including nanostructures.