Continual model of magnetic dynamics for antiferromagnetic particles in analyzing size effects on Morin transition in hematite nanoparticles
Alternative explanation to the effect of disappearance of the Morin transition on hematite nanoparticles with their size decreasing is proposed basing on an idea of the predominant role of the shape anisotropy for nanosize particles. Three types of the magnetic structure of hematite nanoparticles with various sizes are found by Mössbauer spectroscopy: coexistence of the well-pronounced antiferromagnetic and weakly ferromagnetic phases for particles with average diameters of about 55 nm, non-uniform distribution of the magnetization axes which concentrate on the vicinity of the basal plane (111) for prolonged particles with cross sections of about 20 nm, and uniform distribution of the easy axes in regard to the crystalline directions for 3-nm particles. Description of the temperature evolution of experimental data within novel model of the magnetic dynamics for antiferromagnetic particles which accounts the exchange, relativistic, and anisotropy interactions is provided, and the structural as well as energy characteristics of the studied systems are reconstructed.
KeywordsHematite nanoparticles Magnetic dynamics Exchange interaction Dzyaloshinskii–Moriya interaction Shape anisotropy Mössbauer spectroscopy
Authors thank Prof. J. Litterst and Dr. M. Kracken at the Technical University of Braunschweig for the experimental spectra of dextran-coated nanoparticles.
Experimental part of this work (section “Samples and experiment”) was supported by the Russian Ministry for Education and Science, project no. 14.587.21.0027. Theoretical and calculation part (section “Results of analysis”) was carried out under Program of Federal Agency for Scientific Organizations of Russia.
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Conflict of interest
The authors declare that they have no conflict of interest.
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