# Orientation of Magnetic Dipoles

Does a magnetic dipole (in a permanent magnet) tend to align with the B-field or with the H-field?

The current loop (Ampère) model of the magnetic dipole suggests the former, while the magnetic-monopole (Gilbert) model suggests the latter.

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$$\vec{H}=\frac{\vec{B}}{\mu_0}-\vec{M}$$ And since dipole moment is always colinear with itself, aligning with B-field is equivalent to aligning with H-field.

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(If the bar magnet is a very very long, narrow cylinder, polarized along its axis, then the H field is almost 0, so $B/\mu_0$ is almost equal to M.)