當前，柔性磁性元件的應用需求日益增加，這類元件除了需要具備優異的磁性特性外，還必須在反覆彎曲的條件下保持性能穩定。為此，本研究選擇白雲母作為柔性基材。白雲母具有層狀結構、良好的柔韌性和化學穩定性，是一種理想的載體，能夠在保持材料可彎曲特性的同時，提供穩定的基底。通過水熱法將硝酸鈷溶液利用插層的方式嵌入雲母層與層之間，隨後經過不同的退火條件生成四氧化三鈷奈米粒子。這一分層合成方式不僅確保了奈米粒子與基材之間的良好結合，還有助於控制粒子的分佈和尺寸，從而優化其磁性表現。
四氧化三鈷奈米粒子具有鐵磁性，並表現出與其塊材不同的磁性行為。特別是在奈米尺度下，材料的磁性隨著退火溫度的上升而增強，且奈米粒子的粒徑大小會隨著退火溫度的上升而增加。在高於350℃的退火條件下，奈米粒子的粒徑增長趨於平緩，顯示出穩定的尺寸特徵。而材料的矯頑場隨著退火溫度的升高而降低，但在高於500℃退火條件下，矯頑場的變化趨於平緩，顯示出穩定的磁性特徵。
除了磁滯曲線的量測，本研究還進行了彎曲試驗（bending test）、保持測試（retention test）和循環測試（cycle test），以模擬實際應用中的各種操作條件，評估材料在不同彎曲狀態下的磁性變化。實驗結果顯示，該材料在不同的彎曲條件下仍能保持其原有的磁性特徵，這說明白雲母作為柔性基材的優勢，以及水熱法和後續退火製程生成四氧化三鈷奈米粒子的策略是成功的。本研究因而證實了Co₃O₄奈米粒子不僅具有結構穩定性，而且也具有磁性穩定性。這些結果進一步證明了四氧化三鈷在柔性磁性元件中的應用潛力，為高性能柔性磁性元件的開發提供了重要依據，也展示了其在未來電子器件中的廣闊應用前景。

The increasing demand for flexible magnetic devices requires not only excellent magnetic properties but also stable performance under repeated bending conditions. In this study, Muscovite is selected as a flexible substrate due to its layered structure, flexibility, and chemical stability, making it an ideal carrier that preserves the material’s bendability while providing a stable base. Using a hydrothermal method, Cobalt nitrate solution is intercalated between the muscovite layers, followed by annealing under different conditions to generate Cobalt oxide (Co₃O₄) nanoparticles. This layered synthesis approach ensures strong bonding between the nanoparticles and the substrate, and allows for control over particle distribution and size, optimizing magnetic performance.
The Co₃O₄ nanoparticles exhibit ferromagnetic properties, distinct from their bulk counterparts, with magnetism increasing as annealing temperatures rise. Nanoparticle size also increases with higher annealing temperatures but stabilizes beyond 350°C, demonstrating consistent size characteristics. Coercivity decreases with higher temperatures but also plateaus above 500°C, indicating stable magnetic properties.
In addition to measuring magnetic hysteresis loops, bending, retention, and cycle tests are conducted to simulate various operational conditions encountered in practical applications, evaluating the material’s magnetic stability and performance under repeated bending. Results show that the material maintains its original magnetic characteristics under various bending conditions, revealing the advantages of using Muscovite as a flexible substrate. This study thus confirms that Co₃O₄ nanoparticles possess not only structural stability but also magnetic stability. The successful formation of Co₃O₄ nanoparticles through hydrothermal synthesis and subsequent annealing process demonstrate significant potential for Co₃O₄ in flexible magnetic devices, providing a solid foundation for developing high-performance components for future electronic applications.

6參考文獻
[1] M. Zou, Y. Ma, X. Yuan, Y. Hu, J. Liu, and Z. Jin, "Flexible devices: from materials, architectures to applications," Journal of Semiconductors, vol. 39, no. 1, p. 011010, 2018.
[2] H. Yang, Y. Xie, Z. Lu, Z. Wang, and R. Li, "Research progress of flexible magnetic films and devices," Acta Phys. Sin, vol. 71, p. 097503, 2022.
[3] J. Wan, S. D. Lacey, J. Dai, W. Bao, M. S. Fuhrer, and L. Hu, "Tuning two-dimensional nanomaterials by intercalation: materials, properties and applications," Chemical Society Reviews, vol. 45, no. 24, pp. 6742-6765, 2016.
[4] M. Rajapakse et al., "Intercalation as a versatile tool for fabrication, property tuning, and phase transitions in 2D materials," npj 2D Materials and Applications, vol. 5, no. 1, p. 30, 2021.
[5] Y.-C. Chen et al., "Creation of novel composite: Flexible magnetic and conductive muscovite," Materials Today Advances, vol. 20, p. 100423, 2023.
[6] T. D. Ha et al., "Mechanically tunable exchange coupling of Co/CoO bilayers on flexible muscovite substrates," Nanoscale, vol. 12, no. 5, pp. 3284-3291, 2020.
[7] H. Zhu et al., "Optical and electrical properties of ITO film on flexible fluorphlogopite substrate," Ceramics International, vol. 47, no. 12, pp. 16980-16985, 2021.
[8] M. H. Habibi and E. Shojaee, "Bi-component cobalt metatitanate and cobalt oxide nano-composite for high efficient photocatalytic degradation of triazo Direct Blue 71: synthesis, characterization and surface properties," Journal of Materials Science: Materials in Electronics, vol. 28, pp. 11013-11019, 2017.
[9] T. D. Ha et al., "Mechanically tunable exchange coupling of Co/CoO bilayers on flexible muscovite substrates," Nanoscale, vol. 12, no. 5, pp. 3284-3291, 2020.
[10] S. Farhadi, J. Safabakhsh, and P. Zaringhadam, "Synthesis, characterization, and investigation of optical and magnetic properties of cobalt oxide (Co 3 O 4) nanoparticles," Journal of Nanostructure in Chemistry, vol. 3, pp. 1-9, 2013.
[11] M. T. Makhlouf, B. Abu-Zied, and T. Mansoure, "Effect of fuel/oxidizer ratio and the calcination temperature on the preparation of microporous-nanostructured tricobalt tetraoxide," Advanced Powder Technology, vol. 25, no. 2, pp. 560-566, 2014.
[12] 奈米磁性顆粒之置備與應用，研究論文，賴志煌，2003
[13] L. Zhuang et al., "Tuning oxygen vacancies in two-dimensional iron-cobalt oxide nanosheets through hydrogenation for enhanced oxygen evolution activity," Nano Research, vol. 11, pp. 3509-3518, 2018.
[14] Y.-J. Wang et al., "Flexible magnetoelectric complex oxide heterostructures on muscovite for proximity sensor," npj Flexible Electronics, vol. 7, no. 1, p. 10, 2023.
[15] W.-E. Ke et al., "Barium hexaferrite/muscovite heteroepitaxy with mechanically robust perpendicular magnetic anisotropy," npj Flexible Electronics, vol. 5, no. 1, p. 33, 2021.
[16] C. V. Raman and K. S. Krishnan, "A new type of secondary radiation," Nature, vol. 121, no. 3048, pp. 501-502, 1928.
[17] E. Smith and G. Dent, Modern Raman spectroscopy: a practical approach. John Wiley & Sons, 2019.
[18] J. F. Watts and J. Wolstenholme, An introduction to surface analysis by XPS and AES. John Wiley & Sons, 2019.
[19] A. Iglesias‐Juez, G. L. Chiarello, G. S. Patience, and M. O. Guerrero‐Pérez, "Experimental methods in chemical engineering: X‐ray absorption spectroscopy—XAS, XANES, EXAFS," The Canadian Journal of Chemical Engineering, vol. 100, no. 1, pp. 3-22, 2022.
[20] V. Shukla, "Introduction of Vibrating Sample Magnetometer for Magnetic Characterization," in Handbook of Magnetic Hybrid Nanoalloys and their Nanocomposites: Springer, 2022, pp. 483-505.
[21] M. Ghidini, F. Maccherozzi, S. S. Dhesi, and N. D. Mathur, "XPEEM and MFM imaging of ferroic materials," Advanced Electronic Materials, vol. 8, no. 6, p. 2200162, 2022.
[22] M. Kalubowilage, K. Janik, and S. H. Bossmann, "Magnetic nanomaterials for magnetically-aided drug delivery and hyperthermia," Applied Sciences, vol. 9, no. 14, p. 2927, 2019.