The ability of rocks to be magnetized is caused primarily by the magnetic minerals found within them. In the case of transitional metals, such as Fe, Co, and Ni (potential ferromagnets), the magnetic momentums related to the spin of the empty 3d or 4f electron shell have a value other than zero. The reason for the observable spontaneous magnetic orderliness in these ferromagnets is the mutual effect of exchange between the uncompensated magnetic momentums, related to the electron spin of the neighbouring atoms, the magnitude of which can be characterized by the size of the overlapping of the wave functions of the appropriate orbits. Thus, ferromagnetism arises only alongside certain parameters of the crystal structure: when the atom diameter is at least 1.5 times that of the empty 3d or 4f electron shells. This ratio of diameters depends on the constants of the lattice that is on the chemical environment of the magnetizable transitional metal atom. Because the lattice constants depend upon temperature, pressure, and lattice symmetry, so does the ability to be magnetized. In the case of sulphides for example, the maximum magnetization is not with the FeS composition, rather with the Fe1-xS composition. In other words, it is apparently the excess sulphur which increases magnetizability, but it is the bond lengths which have a decisive role. For the same reason, the magnetizability of iron oxides decreases with the increase in the degree of oxidization.
|Number of pages||19|
|Publication status||Published - Dec 28 2011|
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