Try mounting other objects such as aluminum, wood, prunes—yes, even prunes!—on your torsional pendulum. What are their respective magnetic properties?
There are three types of magnetism: diamagnetism, ferromagnetism, and paramagnetism. Iron is ferromagnetic, which means it’s attracted to both poles of a magnet. In atoms of iron, cobalt, and nickel, the spins of electrons in one atom will align with electrons in neighboring atoms, making regions called domains that have very strong magnetization.
The third type of magnetism is paramagnetism. Atoms and molecules that have single, unpaired electrons—such as aluminum, hydrogen, lithium, and liquid oxygen—are paramagnetic. Their electrons orient in a magnetic field, causing them to be weakly attracted to both magnetic poles.
Every electron is a magnet because electrons carry charge and spin. In addition, an electron in orbit can be an electric current, turning the electron into an electromagnet.
To accurately model the behavior of ferromagnetic, diamagnetic, and paramagnetic materials requires quantum mechanics. We encourage you to research this!