My studies around the complex formulated elektrodynamic with complex
refraction index have given a very top result.
The magnetic permeability is the sum of the permeability in vacuum and the
product of the conjungatet
dielectricity constant and a constant which does not depend on the
frequency ( there is another factor i the imaginary unit and Omega, 2 pi
times freuency)

This is a surprising easy thing.

The real part depends on imaginary part of the dielectric constant. Thats
true because magnets are conductors. There also exists an magnetic induced
absorption of energy - the imaginary part is dependant on the real part of
the dielectric function and must be greater zero at all frequencies.

The constant can be determind with the tabled dia - and peramagnetic
coefficients and the conductivity value for direct current. Since the
conductivity is positiv, the sign of that constant determines, weather a
material is diamagnetic or peramagnetic. For these the constant must be
small. If the constant is very big the magnetic field H is not any more
strictly proporitonal to B, therefore the old known effect that ferromagnets
have hysteresis comes out !

The formula fulfills the Cramers - Kronig relations ! What i want to say
here,is, that the cramerd cronig relations seam to be fulfilled fir the
invers 1/permeability. But up to now, this theory is not valid in classical
physics !

But ist behaves otherwise than the old guys believed. When the constant is
not zero the effect runs with mathemacial precition down to higher
frequencies. Therefore also microwave and optical frequencies show
magnetic induced effects and within magnets you have not only one index of
refraction, you have two of them.