Single-domain magnetic particles

Another useful and important example is a single-domain magnetic particle with a uniaxial anisotropy described by the expression... 

FMR spectra of cobalt metal catalysts are shown in Fig. 2. FMR spectroscopy is a useful tool for studying very small magnetic particles. For sufficiently small single-domain magnetic particles, rapid thcimal fluctuations of the magnetization vector tend to average out anisotropic... 

We consider a statistical assembly of disordered single-domain magnetic nanoparticles whose characteristics vary from one particle to another. In a... 

The properties of ferrofluids seem now to be well understood, and numerous applications have been found. Unlike ER and MR fluids, particles in ferrofluids have permanent (magnetic) dipoles thus the particles must be small, around 10 nm, to prevent permanent clumping. If single-domain ferromagnetic particles this small are made, and coated with surfactant to prevent clumping by van der Waals forces, stable ferrofluids can be made whose properties are readily predicted from theory. 

Lederman, M., Schultz S., and Ozaki, M., Investigation of the dynamics of the magnetization reversal in individual single-domain ferromagnetic particles. Phys. Rev. Lett, 73, 1986, 1994. 

Coffey WT, Crothers DSF, Kalmykov YP, Massawe ES, Waldron JT (1993) Exact analytic formulae for the correlation times for single domain ferromagnetic particles. J Magnet Magnetic Mater 127 L254-L260... 

Cregg PJ, Crothers DSF, Wickstead AW (1994) An approximate formula for the relaxation time of a single domain ferromagnetic particle with nniaxial anisotropy and collinear field. J Appl Phys 76 4900-4902 Dang MZ, Rancourt DG (1996) Simnltaneons magnetic and chemical order-disorder phenomena in FesNi, FeNi, and FeNij. Phys Rev B 53 2291-2301... 

Our starting point is the Landau Lifshitz or Gilbert (LLG) equation for the dynamics of the magnetization M of a single-domain ferromagnetic particle, namely [48 51],... 

Figure 1. Variation of the magnetization M, of a single domain ferromagnetic particle with temperature.

The behavior of the magnetization of a single domain ferromagnetic particle has been the subject of much study. Landau and Lifshitz in their 1935 paper [5] gave an equation of motion describing the average... 

Since in a single domain ferromagnetic particle, all the uncompensated electrons are aligned, it is possible to use the above equation of motion, which is for an individual electron, to describe the dynamics of the total magnetization. In so doing we have. 

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