FOMP
The magnetocrystalline anisotropy energy of a ferromagnetic crystal can be expressed as a power series of direction cosines of the magnetic moment with respect to the crystal axes. The coefficient of those terms is the constant ''anisotropy''. In general, the expansion is limited to a few terms. Normally the magnetization curve is continuous with respect to the applied field up to saturation but, in certain intervals of the anisotropy constant values, irreversible field-induced rotations of the magnetization are possible, implying first-order magnetization transition between equivalent magnetization minima, the so-called first-order magnetization process (FOMP). Theory The ''total energy'' of a uniaxial magnetic crystal in an applied magnetic field can be written as a summation of the anisotropy term up to six order, neglecting the sixfold planar contribution, \displaystyle E_A=K_1\sin^2\theta+K_2\sin^4\theta+K_3\sin^6\theta and the field dependent Zeeman energy term \displaysty ...
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