量子尺寸对Eu2MnHfO6纳米颗粒磁性的影响：表面体积比、磁阻塞和磁相变的作用

IF 4.6 2区物理与天体物理 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Results in Physics Pub Date : 2025-06-07 DOI:10.1016/j.rinp.2025.108326

Sibusiso Nqayi, Buyisiwe Sondezi

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引用次数: 0

摘要

本文研究了溶胶-凝胶法制备Eu2MnHfO6 （EMHO）纳米粒子（NPs）并在500、800和1000℃下退火后的量子尺寸效应。XRD证实，所有样品均存在立方Fd3′m结构，NP尺寸从7.4 nm增加到23.8 nm。FTIR光谱显示，较小的NPs表现出量子点（QD）的特征，由于表面配位破坏，Mn/Hf - o - Mn/Hf键变弱。磁性测量揭示了尺寸依赖行为：较小的NPs表现出表面驱动的现象，如阻挡温度（TB）和表面自旋效应（TSE），而较大的NPs （23.8 nm）表现出与不同的nsamel （TN）和Curie （TC）温度相似的体状超交换相互作用。在最小和最大的粒子中发现局部磁不均匀性，表明格里菲斯相（GP），与TC重叠。这些新结果强调了表面与体积比如何影响磁跃迁，支持了修改的居里-魏斯定律，该定律通过MNPs的配位变化区分了表面和体积效应。

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Quantum size effects on magnetism in Eu2MnHfO6 nanoparticles: Role of surface-to-volume ratio, magnetic blocking, and magnetic phase transitions

In this paper, we investigate the quantum size effects on Eu₂MnHfO₆ (EMHO) nanoparticles (NPs) synthesized via sol–gel and annealed at 500, 800, and 1000 °C. XRD confirmed a cubic Fd3̅m structure across all samples, with NP sizes increasing from 7.4 nm to 23.8 nm. Smaller NPs displayed features of quantum dots (QD) and weakened Mn/Hf–O–Mn/Hf bonding due to broken surface coordination, as seen in FTIR spectra. Magnetic measurements revealed size-dependent behaviour: smaller NPs exhibited surface-driven phenomena like blocking temperature (T_B) and surface spin effects (T_SE), while larger NPs (23.8 nm) showed bulk-like super-exchange interactions with distinct Néel (T_N) and Curie (T_C) temperatures. Local magnetic inhomogeneities indicating a Griffiths phase (GP) were found in the smallest and largest particles, overlapping with T_C. These novel results underscore how surface-to-volume ratios influence magnetic transitions, supporting a modified Curie–Weiss law that distinguishes surface and volume effects with coordination variations in MNPs.

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来源期刊

Results in Physics MATERIALS SCIENCE, MULTIDISCIPLINARYPHYSIC-PHYSICS, MULTIDISCIPLINARY

CiteScore

8.70

自引率

9.40%

发文量

754

审稿时长

50 days

期刊介绍： Results in Physics is an open access journal offering authors the opportunity to publish in all fundamental and interdisciplinary areas of physics, materials science, and applied physics. Papers of a theoretical, computational, and experimental nature are all welcome. Results in Physics accepts papers that are scientifically sound, technically correct and provide valuable new knowledge to the physics community. Topics such as three-dimensional flow and magnetohydrodynamics are not within the scope of Results in Physics. Results in Physics welcomes three types of papers: 1. Full research papers 2. Microarticles: very short papers, no longer than two pages. They may consist of a single, but well-described piece of information, such as: - Data and/or a plot plus a description - Description of a new method or instrumentation - Negative results - Concept or design study 3. Letters to the Editor: Letters discussing a recent article published in Results in Physics are welcome. These are objective, constructive, or educational critiques of papers published in Results in Physics. Accepted letters will be sent to the author of the original paper for a response. Each letter and response is published together. Letters should be received within 8 weeks of the article''s publication. They should not exceed 750 words of text and 10 references.