Magnetic dipole interaction
= Magnetic dipole interaction
{title2=$U_{\rm dd}=\frac{\mu_0}{4\pi r^3}[\mathbf m_1\cdot\mathbf m_2-3(\mathbf m_1\cdot\hat{\mathbf r})(\mathbf m_2\cdot\hat{\mathbf r})]$}
The orientation-dependent interaction of two distant localized <magnetic dipole moments>. Its $r^{-3}$ scale makes close approach important in a concentrated magnetic-particle dispersion. Depending on geometry, it can favor chains, collective alignment or frustrated configurations.