Some of the important features of NiZn ferrites are described here in order to give a glimpse of the magnetic properties to our valued customer.


A non-magnetized Ferrite when subjected to an AC magnetic field creates a loop as shown below. At very low fields, the BH relation is reversible and on higher fields the relation becomes non-linear and non-reversible. Saturation magnetization (Bs) represents the saturation limit of flux density and Remanence (Br) is the residual flux even after the withdrawal of the inducing field. Coercivity (Hc) is the magnetic field required in the opposite direction to demagnetize the ferrite.
 

The internal resistance imposed by anisotropy and other pinning centers causes the delay in magnetization. The energy consumed to overcome this resistance is indicated by the area of the BH loop and is called hysterisis loss. Ferrite cores are manufactured as per customer requirements and a wide range of products are available with different sizes and shapes. Correct materials are selected to make the finished ferrite suit all the customer requirements. These materials are tested on a standard toroid and used as a guideline to manufacture the right components.


The most significant property of ferrites, which determines its performance, is the permeability and its response to external factors like Temperature, Frequency and Bias field. Permeability is the ratio of magnetic flux density (B) to the magnetic field causing the flux generation (H). In simple
terms the 'B' is related to 'H' by B = m◦ H where m◦ is the permeability of vacuum, 4p x 10^-7 H/m.

Initial permeability of ferrite material is defined by Initial permeability of ferrite material is defined by

Initial permeability is measured on toroidal cores at very low applied fields. The flux density generated may be less than 0.1 mT. Initial permeability is calculated from the measured value of inductance (L) and calculated value of core factor Ci using the formula

Ferrites when subjected to a magnetizing field induces magnetic flux (f, Webster) and the flux per unit area is the flux density (B,Tesla). As Tesla is a larger unit, a smaller unit ml (=10⁶T) is used for all practical applications. Flux density is the product of permeability and applied field.

Purposefully, an air gap is introduced in the ferrite core for technical benefits. The shearing of the B-H loop helps increase the saturation limit to the core. The permeability of gapped cores (m_e) reduces as a function of the air gap.

It is the ratio of the flux density and the applied field at higher field in the absence of DC bias field.

There are many application conditions where DC bias is applied. The incremental permeability (~t~) is observed when and AC field is superimposed with a DC field.