Answer:
Magnetic materials have many spinning, unpaired electrons.
Step-by-step explanation:
Any moving electric charge creates a magnetic field, also electrons since they spin and move around the nucleus. However, if two electrons are paired on the same orbital they always spin in opposite directions that causes their magnetic field to cancel out. Even if there are unpaired electrons in some atoms and these atoms act as small magnets, the magnetic field of the neighbouring atoms can have different directions and they also cancel out each other. Only presence of a large number of unpaired electrons in a material can create a significant magnetic field. This is the root part of the definition of magnetic properties of material.