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 (μe 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.

(μ0)

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 - -