The Polder tensor is a
tensor introduced by
Dirk Polder[1] for the description of magnetic
permeability of
ferrites.[2] The tensor notation needs to be used because ferrimagnetic material becomes
anisotropic in the presence of a magnetizing field.
Neglecting the effects of damping, the components of the tensor are given by
where
(rad / s) / (A / m) is the effective
gyromagnetic ratio and , the so-called effective
g-factor (physics), is a ferrite material constant typically in the range of 1.5 - 2.6, depending on the particular ferrite material. is the frequency of the RF/microwave signal propagating through the ferrite, is the internal magnetic bias field, is the
magnetization of the ferrite material and is the magnetic
permeability of free space.
To simplify computations, the radian frequencies of and can be replaced with frequencies (Hz) in the equations for and because the factor cancels. In this case, Hz / (A / m) MHz / Oe. If
CGS units are used, computations can be further simplified because the factor can be dropped.