That cooling time frame would not have allowed for meteoric impact magnetization, which usually fades within a day or so, to be locked in, Garrick - Bethell says, pointing to a more permanent internal magnetic field on the moon. (scientificamerican.com)
That implies that the internal magnetic field is «much more complex than people thought» he said. (scientificamerican.com)
But the interaction of the two materials at their interface creates an internal magnetic field that aligns all the atoms in the nickel iron layers. (sciencemag.org)