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The article **Ferromagnetic material properties** is intended to contain a glossary of terms used to describe (mainly quantitatively) ferromagnetic materials, and magnetic cores.

- Hysteresis loop
- Induction B as function of field strength H for H varying between H
_{min}and H_{max}; for ferromagnetic material the B has different values for H going up and down, therefore a plot of the function forms a loop instead of a curve joining two points; for perminvar type materials, the loop is a "rectangle" (*Domain Structure of Perminvar Having a Rectangular Hysteresis Loop*, Williams, Goertz,*Journal of Applied Physics***23**, 316 (1952); in fact it is rectangle if B-μ_{0}H is used instead B on the plot); - Remanence, B
_{r}; "induction which remains" - After magnetization to saturation, a value of induction B in the material in a closed magnetic circuit without external field H; the point where hysteresis loop crosses B axis;
^{[1]}^{: 208 } - Coercivity, H
_{c} - After magnetization to saturation, a value of field strength H at which induction B in the material becomes 0; the point where hysteresis loop crosses H axis;
- Maximum energy product, (BH)
_{max} - Largest possible field of a rectangle on the hysteresis loop plot, which has two edges on the B and H axes, and a vertex on the hysteresis loop in the second quadrant (B positive, H negative); range from below 1 J/m
^{3}for some soft materials (permalloy, 3E4 ferrite), to above 400 kJ/m^{3}for hard ones (neodymium magnets); - Magnetic viscosity
- When an external field H is changed, and then kept at a new value, the induction B first changes almost at once, then some smaller change of B follows in a time; for a permanent magnet typically the time dependence is B(t) = B(t
_{0}) − S·ln(t/t_{0}), where t is time since H change, t_{0}is some reference time, and S is a constant of the process (but not of the material, as it varies with magnitude of the H and its change); a theory describing this kind of time dependency was developed by Louis Néel (*J. de Phys. et Radium*,**11**, 49 (1950)) and by Street and Wooley (A Study of Magnetic Viscosity,*Proc. Phys. Soc.***A62**. 562 (1949)).

To describe a soft ferromagnetic material for technical use, the following parameters are specified:

- (Relative) permeability
- Ratio of induction B in the material caused by some field H to an induction in a vacuum in the same field; it is a dimensionless value, as it is
*relative*to a vacuum permeability;- Initial permeability,
- The ratio for small magnetization of initially demagnetized material: for very small H;
- Incremental permeability,
- The ratio of change of induction in the material to a change of induction in a vacuum due to the same field change, when the change is superimposed to some constant field: ;
- Amplitude permeability,
- The ratio of induction in the material to an induction in a vacuum for larger magnetization: just ;
- Maximum incremental/amplitude permeability
- The maximal value of the incremental/amplitude permeability on the hysteresis curve;

- Saturation induction
- Induction B for large (enough for to become small), but reasonable H;
- Resistivity,
- Specific resistance, as for usual resistive materials, important because of eddy currents; SI units, ohm-metres (Ω·m);
- Mass density
- Mass per unit volume, as for usual materials;
- Temperature factor of the permeability,
- Defined as by IEC133, and as by IEC367-1;
- Curie point (or Curie temperature)
- A temperature, above which the ferromagnetic material becomes a paramagnet; more in ferromagnetism;
- Tangent of loss angle
- Ratio of a resistance (R) to a reactance () of a coil on a core without a gap ( - otherwise it must be scaled), assuming the resistance is result of losses in the magnetic material; the angle describes a delay between B in the material versus H; measured for sinusoidal magnetic field of frequency f; usually specified as
- Disaccommodation factor,
- It is a measure of material permeability variation after demagnetization, given by a formula , where are permeability values, and t
_{1}, t_{2}are time from demagnetization; usually determined for t_{1}= 10 min, t_{2}= 100 min; range from 2×10^{−6}to 12×10^{−6}for typical MnZn and NiZn ferrites; - Hysteresis constant,
- DC sensitivity constant,

- Core constant, C
_{1} - Sum of l/A along magnetic path; l is length of a part of the path, A is its cross-section. The summation of the magnetic path lengths of each section of the magnetic circuit divided by the square of the corresponding magnetic area of the same section;
- Core constant, C
_{2} - Sum of l/A
^{2}along magnetic path; - Effective length of a magnetic path, l
_{e}; - Effective cross-section, A
_{e}; - Effective volume
- ;
- Effective permeability
- For a magnetic circuit constructed with an air gap or air gaps, the permeability of a hypothetical homogeneous material which would provide the same reluctance;

(these "effective" above are sizes of a toroid core made from the same material which has the same magnetic properties as the core);

- Minimum cross-section, A
_{min}; - Inductance factor, A
_{L} - Inductance of one-turn coil, in nH (note inductance L = A
_{L}n^{2}, n is number of turns) Inductance of a coil on a specified core divided by the square of the number of turns. (Unless otherwise specified the inductance test conditions for inductance factor are at a flux density ~10 gauss); - Turns factor,
- Number of turns for 1 mH (note );

These parameters used e.g. in Philips' handbook ^{[2]} and Magnetic Materials Producers Association "Soft Ferrites, A Users Guide".^{[3]}

**^**Ramsden, Edward (2006).*Hall-effect sensors : theory and applications*(2nd ed.). Amsterdam: Elsevier/Newnes. ISBN 978-0-7506-7934-3.**^**Philips' handbook*Components and materials*, Part 4a, Nov 1978, said in accordance with IEC401 and IEC125**^**Magnetic Materials Producers Association "Soft Ferrites, A Users Guide", MMPA SFG-98, 1998