# Linear / nonlinear approximation

## Introduction

The B(H) dependence is generally a nonlinear law, but in some cases this dependence can be approximated by a straight line. This is then the case of a linear approximation.

## Zones with linear approximation

The zone where a linear approximation can be considered depends on the modeled material, as presented in the table below.

Hard material | Soft material |
---|---|

Demagnetization curve (top left quadrant) |
Intermediate curve ( ≈ curve of 1st magnetization) |

## On the topic of permanent magnets …

A linear approximation is well adapted to modern permanent magnets, called rigid magnet for which the linear zone of the B(H) is important.

For less rigid magnets, such as AlNiCo alloys, the linear zone of the B(H) characteristics is reduced. The linear approximation is not suitable for this type of magnet.

Examples of the B(H) characteristics are given in the figure below.