Temperature dependence
المؤلف:
J. M. D. COEY
المصدر:
Magnetism and Magnetic Materials
الجزء والصفحة:
173
18-2-2021
1454
Temperature dependence
Any anisotropy originating from the magnetic dipole interaction will vary with temperature as M2 because the dipole field Hd ∝ Ms and the energy density Ea = −1/2μ0Ms · Hd ∝ M2s .
Single-ion anisotropy due to the crystal field exhibits a j (j + 1)/2 power law at low temperatures for the second-, fourth- and sixth-order terms, which vary respectively as the third, tenth and twenty-first powers of the magnetization; Kj (T )/Kj (0) = Mj (j+1)/2. Close to TC, these turn into Mj power laws. Here is a rare example of an effect whose temperature dependence is determined by symmetry alone.
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