Abstract
The magnetic properties of SrFe12O19 (SFO) hard hexaferrites are governed by the complex relation to its microstructure, determining their relevance for permanent magnets´ applications. A set of SFO nanoparticles obtained by sol–gel self-combustion synthesis was selected for an in-depth structural X-Rays powder diffraction (XRPD) characterization by means of G(L) line-profile analysis. The obtained crystallites´ size distribution reveal a clear dependence of the size along the [001] direction on the synthesis approach, resulting in the formation of platelet-like crystallites. In addition, the size of the SFO nanoparticles was determined by transmission electron microscopy (TEM) analysis and the average number of crystallites within a particle was estimated. These results have been evaluated to illustrate the formation of single-domain state below a critical value, and the activation volume was derived from time dependent magnetization measurements, aiming to clarify the reversal magnetization process of hard magnetic materials.
Highlights
The magnetic properties of SrFe12O19 (SFO) hard hexaferrites are governed by the complex relation to its microstructure, determining their relevance for permanent magnetsapplications
A broad region can be identified below the critical size (DC) in a hard material, and delimited by the so called coherent size (DCOH)[16]: this refers to the minimum volume that demagnetize in a coherent way, denoted as activation volume (VACT) 14
The Rietveld analysis on X-Rays powder diffraction (XRPD) data revealed that crystallite size along the c-axis can be modulated by suitable thermal treatments[6]
Summary
The magnetic properties of SrFe12O19 (SFO) hard hexaferrites are governed by the complex relation to its microstructure, determining their relevance for permanent magnetsapplications. The size of the SFO nanoparticles was determined by transmission electron microscopy (TEM) analysis and the average number of crystallites within a particle was estimated These results have been evaluated to illustrate the formation of single-domain state below a critical value, and the activation volume was derived from time dependent magnetization measurements, aiming to clarify the reversal magnetization process of hard magnetic materials. The crystallinity of such samples depends on the synthesis method, and more detailed analysis is needed, to clarify the relation between crystallite and particle size To disclose this relationship, a careful analysis of crystalline microstructure parameters (i.e., crystallite and particle size, shape) was performed by transmission electron microscopy (TEM) analysis and by combining Rietveld method and line profile analysis of high statistics X-Ray powder diffraction (XRPD) patterns. The reversal magnetization process is investigated, to clarify the relation between morpho-structural characteristics and magnetic behavior
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