Multilevel relaxation model for describing the Mössbauer spectra of nanoparticles in a magnetic field

• Published in: Journal of experimental and theoretical physics 2012-04, Vol.114 (4), p.609-630
• Main Author: Chuev, M. A.
• Format: Article
• Language: English
• Subjects: Analysis; Classical and Quantum Gravitation; Elementary Particles; Magnetic fields; Nanoparticles; Particle and Nuclear Physics; Physics; Physics and Astronomy; Quantum Field Theory; Relativity Theory; Solid State Physics; Solids and Liquids
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776112020185

A theory is developed for the Mössbauer absorption spectra of an ensemble of single-domain particles in a magnetic field. This theory is based on the generalization of a relaxation model with a quantummechanical description of the stationary states of a particle and on the formalism of Liouville operators for describing the hyperfine interaction for a hyperfine field changing in both the magnitude and direction for various stationary states. The general scheme of calculating relaxation Mössbauer spectra in terms of a standard stochastic approach is substantially optimized using operations with block matrices and a unique tridiagonalization of high-rank non-Hermitian matrices with a simple nonorthogonal transformation in the calculation procedure. The resulting model can easily be implemented on a personal computer. It considers the physical mechanisms of formation of a hyperfine structure in a spectrum of nanoparticles in a real situation and self-consistently describes the qualitative features of the nontrivial evolution of spectra with the temperature and the magnetic-field direction and strength, which has been detected in 57 Fe nucleus experiments performed on magnetic nanoparticles for half a century.