Question

Co, \(\mathrm{Fe},\) and \(\mathrm{N}_{1}\) are ferromagnetic. What is the difterence between ferromagnetic and paramagnetic?

Short answer

Ferromagnetic materials, such as Co, Fe, and Ni, have permanent magnetic moments and exhibit strong magnetic ordering, able to retain magnetization without an external field. Paramagnetic materials have temporary magnetization induced by an external field, with no permanent magnetic ordering.

Step-by-step solution

Understanding Ferromagnetism

Ferromagnetism is a property of materials that have permanent magnetic moments, which means that the material can become magnetized and retain its magnetization. This occurs because the atomic or ionic magnetic moments in a ferromagnetic material can align with each other to produce a strong net magnetic field within the material. The alignment is due to the exchange interaction, which is a quantum mechanical phenomenon.

Understanding Paramagnetism

Paramagnetism, on the other hand, occurs in materials that have unpaired electrons and thus have a net magnetic moment. However, the individual magnetic moments of the atoms or ions do not interact strongly with each other and tend not to align spontaneously. In the presence of an external magnetic field, the magnetic moments can be temporarily aligned with the field, but when the external magnetic field is removed, the alignment is usually lost and the material becomes nonmagnetic.

Comparing Ferromagnetism and Paramagnetism

The key difference between ferromagnetism and paramagnetism lies in their magnetic behavior. Ferromagnetic materials exhibit strong attraction to magnetic fields and can retain magnetization after the external magnetic field is removed. Paramagnetic materials are weakly attracted to magnetic fields and do not retain magnetization when the external field is removed. Ferromagnetism is associated with a permanent magnetic ordering of the domains within the material, whereas paramagnetism is induced by the external field and is not permanent.

Key concepts

Magnetic Properties of Materials

Magnetic properties define how a material responds to an external magnetic field and can dictate its use in various applications. At its core, these properties are determined by the alignment of magnetic moments within the material.

In ferromagnetic materials, like iron (Fe), cobalt (Co), and nickel (Ni), there exists a strong interaction between the magnetic moments, resulting in a parallel alignment that produces a significant net magnetic moment. This quality allows ferromagnetic materials to be used in permanent magnets and components of electronic devices.

On the other hand, paramagnetic materials have unpaired electrons leading to non-interactive and randomly oriented magnetic moments. Under the influence of an external magnetic field, these moments align with the field but the effect is temporary and vanishes when the field is removed, making them unsuitable for permanent magnetism, but useful in medical imaging and other applications where a temporary magnetic response is beneficial.

Exchange Interaction

At the heart of magnetic properties lies the exchange interaction, a powerful force that dictates how atomic or ionic magnetic moments in a material orient themselves relative to each other. This quantum mechanical phenomenon is what leads to the ordered magnetic states observed in various materials.

The exchange interaction is repulsive or attractive depending on the relative orientation of the electron spins involved. In ferromagnetic materials, this interaction is strong enough to cause the magnetic moments to align parallel to each other, reinforcing each other to create a substantial net magnetic moment across the material.

Understanding the exchange interaction is critical in materials science and solid-state physics, as manipulating this interaction can lead to the development of new materials with tailored magnetic properties, such as improved storage media or more efficient electrical transformers.

Magnetic Domains

Magnetic domains are small regions within ferromagnetic materials where the magnetic moments of atoms are aligned in the same direction, creating a uniform magnetic field. The boundaries between domains are known as domain walls, which separate regions of differing magnetic orientation.

An unmagnetized ferromagnetic material typically contains many domains with different directions of magnetization, leading to no net magnetic field externally. When an external magnetic field is applied, these domains can shift, grow, or reorient so that more domains align with the field, a process that is crucial for the material to achieve magnetization.

In practical applications, controlling the size and distribution of magnetic domains is vital. In magnetic recording, for example, smaller domains mean higher density of stored information. Understanding magnetic domains also aids in designing materials that are less prone to becoming demagnetized, ensuring the durability and longevity of magnetic devices.