Muscas Giuseppe, Congiu Francesco, Concas Giorgio, Cannas Carla, Mameli Valentina, Yaacoub Nader, Hassan Rodaina Sayed, Fiorani Dino, Slimani Sawssen, Peddis Davide
Department of Physics, University of Cagliari, Cittadella Universitaria Di Monserrato, S.P. 8 Km 0.700, 09042, Monserrato, CA, Italy.
Università Degli Studi Di Cagliari, Dipartimento Di Scienze Chimiche E Geologiche, and INSTM, Cittadella Universitaria Di Monserrato, S.P. 8 Km 0.700, 09042, Monserrato, CA, Italy.
Nanoscale Res Lett. 2022 Oct 11;17(1):98. doi: 10.1186/s11671-022-03737-w.
Despite modern preparation techniques offer the opportunity to tailor the composition, size, and shape of magnetic nanoparticles, understanding and hence controlling the magnetic properties of such entities remains a challenging task, due to the complex interplay between the volume-related properties and the phenomena occurring at the particle's surface. The present work investigates spinel iron oxide nanoparticles as a model system to quantitatively analyze the crossover between the bulk and the surface-dominated magnetic regimes. The magnetic properties of ensembles of nanoparticles with an average size in the range of 5-13 nm are compared. The role of surface anisotropy and the effect of oleic acid, one of the most common and versatile organic coatings, are discussed. The structural and morphological properties are investigated by X-ray diffraction and transmission electron microscopy. The size dependence of the surface contribution to the effective particle anisotropy and the magnetic structure are analyzed by magnetization measurements and in-field Mössbauer spectrometry. The structural data combined with magnetometry and Mössbauer spectrometry analysis are used to shed light on this complex scenario revealing a crossover between volume and surface-driven properties in the range of 5-7 nm.
尽管现代制备技术为定制磁性纳米颗粒的组成、尺寸和形状提供了机会，但由于与体积相关的性质和在颗粒表面发生的现象之间存在复杂的相互作用，理解并因此控制这些实体的磁性仍然是一项具有挑战性的任务。目前的工作研究尖晶石铁氧化物纳米颗粒作为一个模型系统，以定量分析体相和表面主导的磁态之间的转变。比较了平均尺寸在5-13纳米范围内的纳米颗粒集合体的磁性。讨论了表面各向异性的作用以及油酸（最常见且用途广泛的有机涂层之一）的影响。通过X射线衍射和透射电子显微镜研究了结构和形态性质。通过磁化测量和场内穆斯堡尔光谱分析了表面对有效颗粒各向异性和磁结构贡献的尺寸依赖性。结合结构数据与磁强计和穆斯堡尔光谱分析，以阐明这一复杂情况，揭示在5-7纳米范围内体积和表面驱动性质之间的转变。
