Occupation distribution analysis of Co in La-Co substituted M-type hexaferrite and its significant effect on magnetic properties

• Published in: Journal of alloys and compounds 2024-10, Vol.1003, p.175659, Article 175659
• Main Authors: Liu, Ruoshui, Yu, Xiang, Sun, Yang, Liu, Dan, He, Shiyue, Xu, Juping, Yin, Wen, Zhao, Tongyun, Hu, Fengxia, Zheng, Xinqi, Wang, Lichen, Shen, Baogen
• Format: Article
• Language: English
• Subjects: Co occupation sites; La-Co co-substitution; Magnetocrystalline anisotropy; Neutron diffraction; Permanent magnet ferrite; Single crystal
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.175659

In recent years, La-Co co-substituted M-type strontium hexaferrite (La-Co SrM) has gained significant attention due to its improved permanent magnet performance and elevated operating temperature. However, the occupation of Co ions within the lattice of La-Co SrM has sparked considerable debate over the past two decades. To address this, neutron powder diffraction and Raman spectroscopy were employed in this study to analyze Co occupancy in La-Co SrM single crystal and polycrystalline samples. Results consistently reveal a preference for most Co ions to occupy the spin-down tetrahedral 4f1 site, which enhances the net magnetic moment and uniaxial magnetic anisotropy. Differences in Co ion distribution between single crystals (octahedral 12k and 2a sites) and polycrystalline powders (bipyramidal 2b sites) are attributed to sample preparation conditions, often overlooked in previous discussions. Therefore, precise regulation of Co occupancy, particularly maximizing the occupation of the 4f1 site, proves pivotal in enhancing magnetic properties. •To address Co ion occupancy in La-Co SrM, we used neutron diffraction and Raman spectroscopy on polycrystalline and single crystal samples.•Analysis of Co ion occupancy in these samples revealed identical primary occupancy but distinct secondary occupancy.•Visualizing local deformation at the primary occupancy site, (4f1) provides new insights into its correlation with enhanced magnetic anisotropy.•Understanding the significance of sample preparation in determining Co ions distribution highlights the need for precise experimental control.•Maximizing Co ion occupation at the 4f1 site in La-Co SrM can enhance magnetic properties, offering potential practical applications.