What is Paramagnetism?
Paramagnetism is a form of magnetism where certain materials are weakly attracted by an externally applied magnetic field. Unlike ferromagnetism, paramagnetic materials do not retain any magnetization in the absence of an external field and are not capable of forming permanent magnets. This phenomenon arises from the presence of unpaired electrons within the atoms, ions, or molecules of the material.
Key Principles and Electron Configuration
The fundamental principle behind paramagnetism lies in the quantum mechanical property of electron spin. Electrons possess a magnetic dipole moment due to their spin. In most materials, electrons are paired with opposite spins, canceling out their magnetic moments. However, in paramagnetic materials, there are one or more unpaired electrons whose spins are not canceled, leading to a net magnetic moment for the atom or molecule.
A Practical Example: Oxygen Gas
A common example of a paramagnetic substance is liquid oxygen (O₂). Although one might expect oxygen to be diamagnetic based on its electron configuration, molecular orbital theory reveals that oxygen has two unpaired electrons in its outermost orbitals. When placed in a strong magnetic field, liquid oxygen is visibly attracted to the poles, demonstrating its paramagnetic nature.
Importance and Applications
Understanding paramagnetism is crucial in various scientific fields. In chemistry, it helps in characterizing the electronic structure of molecules and coordination complexes, particularly through techniques like Electron Paramagnetic Resonance (EPR) spectroscopy. In physics and materials science, it contributes to the development of new materials with specific magnetic properties for applications in magnetic resonance imaging (MRI) and quantum computing.