Magnetic behavior of nanofilms prepared by assembling different Co ferrite nanoparticles

IF 5.7 3区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY Materials Research Bulletin Pub Date : 2025-04-01 Epub Date: 2024-11-25 DOI:10.1016/j.materresbull.2024.113229

Viviana B. Daboin , Julieta S. Riva , Paula G. Bercoff

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Abstract

We study the magnetic characteristics of nanofilms composed of CoFe₂O₄ nanoparticles synthesized by thermal decomposition (TD) and self-combustion (SC) methods, assembled on glass substrates using the Langmuir-Blodgett technique. Despite both synthesis methods render crystalline Co ferrite nanoparticles, the differences in particle size and saturation magnetization are notable; however, both nanofilms reveal a ferrimagnetic behavior and display a significant surface contribution to the net magnetization at temperatures below 50 K. This effect is attributed to the nanoparticles' surface spins misaligning with the spins of the ordered core and freezing into a disordered structure. Effective anisotropy K_eff values were determined, obtaining similar values to the bulk material (K_eff ∼2 × 10⁵ J/m³) for the nanofilm made of TD nanoparticles, while the nanofilm prepared with SC nanoparticles presents an enhanced value (K_eff=5 × 10⁵ J/m³). The temperature-dependent saturation magnetization curves were fitted with the modified Bloch's law and an additional term that corresponds to the frozen spins.

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不同钴铁氧体纳米粒子组装制备的纳米膜的磁性行为

本文研究了热分解（TD）和自燃（SC）方法合成的CoFe2O4纳米粒子组成的纳米膜的磁性特征，并利用Langmuir-Blodgett技术组装在玻璃基板上。尽管这两种合成方法都能得到结晶的钴铁氧体纳米颗粒，但在粒径和饱和磁化强度方面存在显著差异；然而，在低于50 K的温度下，两种纳米膜都显示出铁磁性行为，并显示出显著的表面对净磁化的贡献。这种效应是由于纳米粒子的表面自旋与有序核心的自旋不对齐而冻结成无序结构。测定了有效各向异性Keff值，TD纳米颗粒制备的纳米膜的有效各向异性Keff值与块状材料相似（Keff ~ 2 × 105 J/m3），而SC纳米颗粒制备的纳米膜的有效各向异性Keff值增强（Keff=5 × 105 J/m3）。用修正的布洛赫定律拟合了温度相关的饱和磁化曲线，并增加了一个对应于冻结自旋的附加项。

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来源期刊

Materials Research Bulletin 工程技术-材料科学：综合

CiteScore

9.80

自引率

5.60%

发文量

372

审稿时长

42 days

期刊介绍： Materials Research Bulletin is an international journal reporting high-impact research on processing-structure-property relationships in functional materials and nanomaterials with interesting electronic, magnetic, optical, thermal, mechanical or catalytic properties. Papers purely on thermodynamics or theoretical calculations (e.g., density functional theory) do not fall within the scope of the journal unless they also demonstrate a clear link to physical properties. Topics covered include functional materials (e.g., dielectrics, pyroelectrics, piezoelectrics, ferroelectrics, relaxors, thermoelectrics, etc.); electrochemistry and solid-state ionics (e.g., photovoltaics, batteries, sensors, and fuel cells); nanomaterials, graphene, and nanocomposites; luminescence and photocatalysis; crystal-structure and defect-structure analysis; novel electronics; non-crystalline solids; flexible electronics; protein-material interactions; and polymeric ion-exchange membranes.