Magnetic Susceptibility: Definition, Formula, Types, and Applications

Magnetic Susceptibility Definition

Magnetic susceptibility refers to a material’s propensity to become magnetized when exposed to an external magnetic field.

What is Magnetic Susceptibility?

Magnetic susceptibility is a fundamental concept in chemistry and physics that allows us to understand how materials respond to the influence of magnetic fields. This article provides an in-depth exploration of magnetic susceptibility, including its definition, formula, SI unit, various types, the relationship between susceptibility and permeability, the specific case of paramagnetic materials and superconductors, and diverse applications of magnetic susceptibility.

Magnetic susceptibility formula

The formula of magnetic susceptibility (χ) is the ratio of magnetization (M) to the applied magnetic field intensity (H), expressed as χ = M/H.

Magnetic susceptibility si unit

Magnetic susceptibility is a dimensionless quantity and, therefore, does not possess a specific SI unit. It is expressed solely as a numerical value without any accompanying unit.

Types of Magnetic Susceptibility

 1. Paramagnetic Susceptibility

Paramagnetic materials exhibit a positive magnetic susceptibility (χ > 0) and align with the applied magnetic field.

Paramagnetic materials weakly attract magnetic fields and display small positive susceptibility values.

Examples of paramagnetic materials include alkaline earth metals, aluminum, and oxygen.

2. Diamagnetic Susceptibility

Diamagnetic materials possess a negative magnetic susceptibility (χ < 0) and align against the applied magnetic field.

Diamagnetic materials weakly repel magnetic fields and exhibit negative susceptibility values.

Diamagnetic materials encompass gold, tin, mercury, water, copper, zinc, bismuth, and several others.

3. Ferromagnetic Susceptibility

Ferromagnetic materials possess a high positive magnetic susceptibility (χ > 0) and exhibit strong magnetization in the presence of a magnetic field.

Ferromagnetic materials are highly attracted to magnetic fields and retain magnetization even after the external field is removed.

Iron, cobalt, nickel, and their alloys are prominent examples of ferromagnetic materials.

Magnetic Susceptibility and Permeability

Magnetic susceptibility and permeability are interrelated through the equation μ = μ₀(1 + χ), where μ represents the permeability and μ₀ signifies the permeability of free space. Magnetic susceptibility influences the permeability of a material, determining how effectively magnetic flux can permeate it.

Magnetic Susceptibility of Superconductors

Superconductors exhibit perfect diamagnetism, with a magnetic susceptibility of χ = -1.

Superconductors expel magnetic fields from their interior, known as the Meissner effect.

Superconductors display zero electrical resistance and complete magnetic flux exclusion when cooled below their critical temperature.

Applications of Magnetic Susceptibility

Material Characterization: Magnetic susceptibility is crucial for characterizing and categorizing materials based on their magnetic properties.

Magnetic Resonance Imaging (MRI): MRI utilizes the magnetic susceptibility of tissues to generate detailed images of the human body, enabling precise diagnostic imaging.

Geology and Mineralogy: Magnetic susceptibility measurements play a significant role in the field of geology and mineralogy. By assessing the magnetic susceptibility of rocks and minerals, geologists can identify different formations, study magnetic anomalies, and determine the presence of valuable resources.

Material Testing and Quality Control: Magnetic susceptibility testing is employed in various industries for material testing and quality control purposes. It helps assess the magnetic properties of materials such as metals, alloys, and composites, ensuring they meet specific requirements and standards.

Environmental Studies: Magnetic susceptibility measurements are utilized in environmental studies, particularly in the assessment of soil contamination. By examining the magnetic susceptibility of soil samples, scientists can detect the presence of magnetic particles and identify potential pollution sources.

Archaeology and Paleomagnetism: Magnetic susceptibility is utilized in archaeology and paleomagnetism to investigate ancient artifacts and geological formations. By analyzing the magnetic susceptibility of archaeological remains or sedimentary layers, researchers can gain insights into past magnetic fields and geochronology.

Petrophysics and Oil Exploration: Magnetic susceptibility measurements are essential in petrophysics, where they assist in characterizing subsurface rock formations. In oil exploration, magnetic susceptibility data can help identify potential hydrocarbon reservoirs and assess their properties.

Magnetic Material Design and Engineering: Magnetic susceptibility plays a crucial role in the design and engineering of magnetic materials. By understanding the susceptibility characteristics, engineers can develop materials with specific magnetic properties for various applications, such as magnets, transformers, and electronic devices.

Magnetic susceptibility provides valuable insights into how materials interact with magnetic fields. Whether it is understanding the behavior of paramagnetic, diamagnetic, or ferromagnetic materials, or exploring the unique properties of superconductors, magnetic susceptibility plays a pivotal role in multiple scientific and technological fields. From medical imaging and geology to material testing and environmental studies, its applications are diverse and far-reaching. By harnessing the knowledge of magnetic susceptibility, researchers and engineers continue to advance our understanding of materials and their magnetic behavior, leading to innovative developments in various industries.