Diamagnetic materials are those that will repel magnetic fields. Many common materials such as water are diamagnetic, but the effect is usually so weak that only super strong magnetic fields will cause any noticeable effect.
The famous experiment where scientists were able to levitate small animals such as frogs used an incredibly powerful electromagnet to create a magnetic field strong enough to cause the water in the animals to be repelled. Electromagnets like this one draw huge amounts of electric current and therefore need extensive cooling. The structure its self must be very strong to prevent it from crushing its self. This makes it virtually impossible for such an experiment to be done at home or in the school science class.
The experiment shown here does not cause a diamagnetic material to levitate, but it is used to help levitate a small magnet. The diamagnetic material used is Bismuth as it is one of the best diamagnetic materials available.
Bismuth can be obtained from most 'Lead Free' fishing weights or gun shot. It is very similar to lead, and can be melted easily. For this experiment it is necessary to create two blocks of bismuth. When a small magnet is placed between these blocks it will experience a small force from above and below. These forces alone are too weak to lift the magnet so some larger magnets can be placed above to help counteract gravity.
The large magnets are placed on a screw mechanism so that hey can be finely adjusted in height. It will need to be carefully adjusted until the magnet begins to levitate. The space between the two pieces of Bismuth should only be a tiny bit larger then the magnet in between.