A Theoretical Study of Orientational Magnetization Process of Sedimentary Rocks in Cluster Model Approximation

Prof. Vladimir ShashkanovThe cluster model of sedimentary magnetism (V.A. Shashkanov, A.I. Novoselov) formulated in the 1980ies and a theory of orientational magnetization of sediments (V.A. Shashkanov, A.I. Novoselov and A.V. Smirnov) based on this model have formed a basis for the following laboratory investigation of magnetization processes in sediments. However, the problem of the exact type of orientational magnetization Jro(H) field dependency was practically not studied in the cluster theory until now. In an approximation, similar to that of paramagnetic gas, "experimentally found" dependency of Langevin type was accepted as a basic type:

,

where - Jromax is a orientational magnetization maximum value, Hint is an effective field arising from magnetic interactions between clustered grains of magnetic material in the process of precipitation.

However, a number of experiments with artificial sediments deposited in known laboratory conditions with the magnetic grains in known magnetic states has shown that the interaction field values calculated from experimental field dependencies in Langevin approximation are about one order of magnitude less than those resulting from the direct calculation of possible inter-grain interaction fields in clusters. In this connection, the direct calculations of Jro field dependences have been carried out by the two techniques (static and dynamic) within the framework of cluster model. Calculated Jro(H) curves appeared to be approximated much more closely by a hyperbolic tangent

,

than by a Langevin function. A comparison of experimental data for artificial sediments with the results of Langevine and hyperbolic tangent approximations, respectively, has shown that the latter describes much better real "magnetic" conditions in clusters.


V.A. Shashkanov,  A.A. Kosterov,  P.V.Dubrovin

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