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Properties of Soft Magnetic Materials

Magnetics(tm) company ferrite image - RF CafeAfter 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.
  • Bmax:  Saturation Flux Density = maximum flux density that a magnetic material can accommodate; beyond
               Bmax, 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 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.


Material
Initial
Perm.
0)

Bmax
kGauss
Loss Coefficients Curie
Temp
°C

Resistivity
(ohm-cm)
μ0 x Q
@
100 kHz

Operating
Frequencies
e x 106 a x 103 c x 103
Fe 250 22 - - - 770 10 · 10-6 - 60-1,000 Hz
Si-Fe (unoriented) 400 20 870 120 75 740 50 · 10-6 - 60-1,000 Hz
Si-Fe (oriented) 1500 20 - - - 740 50 · 10-6 - 60-1,000 Hz
50-50 Ni Fe (grain-oriented) 2000 16 - - - 360 40 · 10-6 - 60-1,000 Hz
79 Permalloy 12000
to
100000
8
to
11
173 - - 450 55 · 10-6 8000
to
12000
1 kHz
to
75 kHz
Amorphous Alloy B 3,000 15-16 - - - 370 135 · 10-6 - to 250 kHz
Amorphous Alloy E 20,000 5-6.5 - - - 205 140 · 10-6 - to 250 kHz
Permalloy powder 14
to
550
3 0.01
to
0.04
0.002 0.05
to
0.1
450 1 10000 10 kHz
to
1 MHz
High Flux powder 14
to
160
15 - - - 360 - - 10 kHz
to
1 MHz
Kool Mu powder 26
to
125
10 - - - 740 - - to 10 MHz
Iron powder 5
to
80
10 0.002
to
0.04
0.002
to
0.4
0.2
to
1.4
770 104 2000
to
30000
100 kHz
to
100 MHz
Ferrite-MnZn 750
to
15000
3
to
5
0.001 0.002 0.01 100
to
300
10
to
100
100000
to
500000
10 kHz
to
2 MHz
Ferrite-NiZn 10
to
1500
3
to
5
- - - 150
to
450
106 30000 200 kHz
to
100 MHz
Co-Fe 50% 800 24 - - - 980 70 · 10-6 - -

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