Linear dynamic susceptibilities orientation

To summarize this part of the chapter, we have constructed a consistent theory of linear and cubic dynamic susceptibilities of a noninteracting superparamagnetic system with uniaxial particle anisotropy. The scheme developed was specified for consideration of the assemblies with random axis distribution but may be easily extended for any other type of the orientational order imposed on the particle anisotropy axes. A proposed simple approximation is shown to be capable of successful replacement of the results of numerical calculations. 

B. Linear and Cubic Dynamic Susceptibilities of a Dipolar Suspension Effect of Mechanical Orientation... 

In Section IV.B a procedure of numerical solution for Eq. (4.329) is described and enables us to obtain the linear and cubic dynamic susceptibilities for a solid system of uniaxial fine particles. Then, with allowance for the polydispersity of real samples, the model is applied for interpreting the magnetodynamic measurements done on Co-Cu composites [64], and a fairly good agreement is demonstrated. In our work we have proposed for the low-frequency cubic susceptibility of a randomly oriented particle assembly an interpolation (appropriate in the whole temperature range) formula... 

Figure 4.32. Linear dynamic magnetic susceptibilities of a randomly oriented super-paramagnetic assembly (a, b) and of a magnetic fluid of the same particles (c, d) for all the graphs the ratio TdAb = 10-4. Vertical axes for % are scaled in the units of cp2/r so that at to —> 0 both % tend to 1/3.

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