Question

 

What is the difference between a paramagnetic and a diamagnetic material? Do paramagnetism and diamagnetism give strong or weak effects? Give some examples of para and diamond magnets. What do you think happens if you place a small diamagnet (such as a very small piece of graphite) on top of a very strong magnetic field?

Answer 1

Paramagnetic:

Paramagnetism occurs due to the presence of unpaired electrons in the system. Each element has a different number of electrons, and that defines its chemical character. According to how these electrons fill into the energy levels around the nucleus of the respective atom, some electrons remain unpaired. These unpaired electrons act like little magnets causing magnetic properties under the influence of an externally applied magnetic field. Actually, it’s the spin of these electrons that causes magnetism.

Paramagnetic materials have permanent dipole magnetic moments due to the spin of the unpaired electrons even during the absence of an external magnetic field. But these dipoles orient themselves randomly due to thermal motion hence giving a zero net dipole magnetic moment. When we apply an external magnetic field, the dipoles tend to align in the direction of the applied magnetic field resulting in a net dipole magnetic moment. Therefore, paramagnetic materials slightly get attracted to the external magnetic field. But, the material does not retain magnetic properties once we remove the external field. Only a small induced magnetization creates even in the presence of an external magnetic field. This is because, only a small fraction of spins orients with the external magnetic field. Also, this fraction is directly proportional to the strength of the field created.

Diamagnetic:

Some materials tend to show a repelled magnetic behaviour when put in contact with an external magnetic field. These are the diamagnetic materials. They create magnetic fields that are opposing in the direction of the external magnetic field and hence show the repelling behavior. Generally, all materials have the diamagnetic properties, making a weak contribution to the magnetic behaviour of the material when subjected to an external magnetic field. But, in materials that show other magnetic properties such as paramagnetism and ferromagnetism, the effect of diamagnetism is negligible. Due to its weak magnetic property, the effects of diamagnetism is difficult to observe. ‘Bismuth’ acts as a strong diamagnet.

Temperature Dependence:

However Diamagnetic is independent of temperature. its susceptibility does not change with temperature.

Placing Diamagnetic Material in Strong Magnetic Fields:

Advancements in the development of permanent magnets and diamagnetic materials such as pyrolytic graphite have produced a simple method of diamagnetic levitation by simply placing a thin piece of pyrolytic graphite over a strong rare-earth magnet. The pyrolytic graphite is levitated above the magnet.