Methods of Simulating Superparamagnetic Relaxation Mössbauer Spectra and Attempts of Foundation of a Microscopic Theory of Superparamagnetism
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- 作者：H.-D. Pfannes ; J. H. Dias Filho ; R. Paniago and R. Magalh?es-Paniago
- 关键词：superparamagnetism ; M?ssbauer spectroscopy ; spin ; relaxation
- 刊名：Hyperfine Interactions
- 出版年：2003
- 出版时间：2003
- 年：2003
- 卷：148/149
- 期：1/4
- 页码：243-252
- 全文大小：127 KB
文摘
A spin-Hamiltonian that describes the orientational energy of nanoscopic magnetic particles is presented. A few short observations on spin tunneling are made. Basic ideas on superparamagnetism and classical results of calculations of relaxation times are presented. A model for spin–phonon interaction induced spin reversals is proposed and the relaxation time for spin jumps between next nearest spin levels (ΔS z =¡À2) is calculated. M?ssbauer patterns are simulated by means of a multi-level method for spin transitions between next nearest and nearest (ΔS z =¡À1) spin levels. The simulations with (ΔS z =¡À1) show better concordance with experimental spectra and allow the use of a reduced spin, which speeds up considerably the calculations and allows to include particle size distribution.