PX157 - C10d - ferromagnetic materials

$μ_{r} >> 1 :$ magnetic field is greatly amplified
atomic $\vec{μ}$ ordered in domains
$μ_{r} \approx 10^{3}$ , but the value changes with the applied magnetic field, ie: material is non-linear:

\vec{B} = μ_{r} (B_{0}) {\vec{B}}_{0}

when placing a ferromagnetic material into a solenoid:

\vec{B} = μ_{r} μ_{0} n I \hat{z}

magnetization, $\vec{M}$ , may show hysteresis

hard ferromagnetic

permanent magnets which maintain a magnetic field even if ${\vec{B}}_{0} = 0$
$μ_{r}$ cannot be defined