Properties of Soft Magnetic Materials

After recently reading a few articles on ferromagnetic materials for both power supply and RF balun use, I did a little research to find some good sources for information. This table of parameters on common soft magnetic materials is derived from a page in a whitepaper on the Magnetics website. The paper contrasts properties of powdered magnetics, which are composed almost totally of ferrous metal (iron, nickel, cobalt, manganese, et al), versus ferrites, which are a mix of ferrous metal and oxides.

The following table of data listing properties of soft magnetic materials was derived from a "A Critical Comparison of Ferrites with Other Magnetic Materials," on the Magnetics™ website.

Definitions of parameters are as follows:

• Initial Permeability:  ratio between the field B (induction) and the field H (A/m during magnetization) measured when

             the field H is close to zero.

• B_max:  Saturation Flux Density = maximum flux density that a magnetic material can accommodate; beyond

             B_max, further increases in H result in no significant increase in B.

• Loss Coefficients:  e = eddy current,  a = hysteresis coefficient,  c = residual loss
• Curie Temperature:  temperature at which a ferromagnetic material loses its ferromagnetism and becomes

             paramagnetic (μ_e approaches 1).

• μ₀ x Q:  figure of merit (product of μ and Q) for linear core materials. At frequencies of 100 kHz and above,

             the value for ferrites is considerably above all other materials.