What is it called when a group of atoms align their magnetic poles

It is called Magnetic Domain.

Explanation:

This simply explains that when magnetic moment of a group of atoms in a certain material that is magnetic is aligned in one direction or their magnetic poles.

In materials with  ferromagnetic compositions, certain groups of atoms band together into areas which are known to be domains; in this domains, all the electrons posses the same magnetic orientation. In a lot of materials, arrangement of atoms are in a way that the magnetic orientation of one electron cancels out the orientation of another.