Paramagnetic vs Diamagnetic
Materials tend to show weak magnetic properties in the presence of an externally applied magnetic field. Some materials are attracted by the external magnetic field, whereas some are repelled by the external magnetic field. Due to this magnetic behaviour, elements and compounds can be categorized as two types, namely ‘paramagnetic’ and ‘diamagnetic’ Materials that are attracted by external magnetic fields are called ‘Paramagnetic’ and materials that are repelled by external magnetic fields are called ‘Diamagnetic’.
More on Paramagnetism
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 are left unpaired. These unpaired electrons act as 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 an external magnetic field is applied, the dipoles tend to align in the direction of the applied magnetic field resulting in a net dipole magnetic moment. Therefore, paramagnetic materials are slightly attracted by the external magnetic field and the material does not retain magnetic properties once the external field is removed. Only a small induced magnetization is created even in the presence of an external magnetic field, and this is because only a small fraction of spins is oriented by the external magnetic field. This fraction is directly proportional to the strength of the field created.
Generally, higher the no. of unpaired electrons, higher the paramagnetism and higher the strength of the field created. Therefore, transition and inner transition metals show stronger magnetic effects due to the localization of ‘d’ and ‘f’ electrons and also due to the presence of multiple unpaired electrons. Some commonly known paramagnetic elements include Magnesium, Molybdenum, Lithium, and Tantalum. There are also stronger synthetic paramagnets such as ‘ferrofluids’.
More on Diamagnetism
Some materials tend to show a repelled magnetic behaviour when put in contact with an external magnetic field. These are said to be diamagnetic, and they create magnetic fields that are opposing in the direction to the external magnetic field and hence the repelling. Generally all materials have 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.
What is the difference between Paramagnetism and Diamagnetism?
• Paramagnetic materials are attracted by external magnetic fields whereas diamagnetic materials are repelled.
• Paramagnetic materials have at least one unpaired electron in the system, but diamagnetic materials have all their electrons paired.
• The magnetic field created by paramagnetic materials are in the direction of the external magnetic field whereas the magnetic field created by diamagnetic materials are opposing in direction to the external magnetic field.
• Paramagnetism is a stronger magnetic behaviour exhibited only by selective materials, whereas diamagnetism is a weak magnetic behaviour generally shown by all materials and easily suppressed in the presence of stronger magnetic properties.