# What's the magnetic moment induced by an external magnetic field on a ferromagnetic material?

How do you model the magnetic moment that's induced by an external magnetic field? So basically if you have an external B field, and we put a ferromagnetic rod in that field, what would be the rod's magnetic moment?

## 1 Answer

First you need to find the magnetization $M$, this is equal to $\chi_mH$ where $H=\frac{B}{\mu}$. Then the magnetic moment is just $\iiint{MdV}$, over the volume of the rod.

• The problem is that $M = \chi_mH$ applies only in diamagnets and paramagnets. But my rod is made of iron, a ferromagnetic material. Do you have any idea of the link between $M$ and the H field with ferromagnetic materials? – E. Morell Mar 30 '17 at 19:25
• You'll need to refer to the hysteresis curve of that particular ferromagnetic material. – GeeJay Mar 31 '17 at 12:04