Paramagnetic Materials

Paramagnetic Materials are those materials that get weakly magnetized when exposed to the external magnetic field. The spin of the paramagnetic materials are randomly oriented and they get arranged in the direction of the external magnetic field. They lose their magnetic properties when the external magnetic field is removed. Paramagnetic Materials are important in the field of material science as they are used for various applications

In this article, we will learn about Paramagnetic Materials, their properties, examples, applications, and how they are different from Diamagnetic Materials and Ferromagnetic Materials.

What are Paramagnetic Materials?

Paramagnetic Materials are materials that get weakly magnetized in the direction of the external magnetic field when placed in a magnetic field. They have a permanent Dipole moment. They have some unpaired electrons, and due to this, the net magnetic moment of all electrons is not added up to zero.

Learn,

• Magnetism
• Dipole Moment

Paramagnetic Material Definition

Paramagnetic Materials are defined as the materials which get weakly magnetized in the direction of external magnetic field and lose their magnetic property when removed from external magnetic field

Paramagnetic Material Examples

Examples of Paramagnetic Materials are,

• Aluminum (Al)
• Platinum (Pt)
• Copper (Cu)
• Graphite
• Oxygen (O₂)
• Manganese (Mn)
• Chromium (Cr)

Properties of Paramagnetic Materials

The properties of Paramagnetic Materials are mentioned below:

1. Although the net atomic dipole moment of an atom is not zero, atoms of paramagnetic substances have a permanent dipole moment due to unpaired electron spin.
2. These objects are weakly attracted by magnets most of the times.
3. The paramagnetic rod aligns itself with the magnetic field because the magnetic field is stronger near the pole compared to that of along the body.
4. Magnetization is very small, positive and proportional to the magnetization field.
5. Magnetic susceptibility is very small.
6. The relative magnetic permeability is slightly less than 1. The magnetic field in the material is larger than the magnetization field.
7. The internal magnetic field lines of paramagnetic substances intensify.
8. The magnetization intensity of a paramagnetic substance is inversely proportional to temperature. Paramagnetic substances follow Curie's law, which says that magnetic susceptibility is inversely proportional to temperature.

Curie Temperature for Paramagnetic Material

The curie temperature for different paramagnetic material is tabulated below:

Substance	Curie Temperature
Aluminum (Al)	660.32°C or 1220.58°F
Platinum (Pt)	1772°C or 3222°F
Copper (Cu)	1358°C or 2476°F
Oxygen (O2)	-183°C or -297°F

Spin structure of Paramagnetic Material

The spin patterns of paramagnetic materials are different from those of ferromagnetic or antiferromagnetic materials. In paramagnetic materials, the magnetic moments of individual atoms or ions are randomly oriented, resulting in the absence of all magnetism. Unlike ferromagnets (in which adjacent magnetic fields are parallel) or antiferromagnets (in which adjacent magnetic fields are antiparallel), paramagnetic materials do not choose the best of their magnetic times.

Random orientation: In paramagnetic materials, the magnetic moment associated with individual atoms or ions is randomly oriented due to thermal motion. Thermal energy above the Curie temperature, or magnetic order temperature of the material, is sufficient to overcome any affinity.

No magnetic properties: Unlike ferromagnetic materials, which have positive magnetic properties and magnetic moments, paramagnetic materials do not have these properties. Lack of coordination results in a weak, transient response to the external magnetic field.

Magnetic susceptibility: Paramagnetic materials show magnetic susceptibility, which means that they can be weakly magnetized in the presence of an external magnetic field. However, when the external magnetic field is removed, the magnetic moment returns to its random direction.

Types of Paramagnetic Materials

There are two types of Paramagnetic Materials

• Intrinsic Paramagnet
• Extrinsic Paramagnet

Intrinsic Paramagnets

The paramagnetic properties of intrinsic paramagnetic materials result from the presence of unpaired electrons in their atomic or molecular orbitals. Examples of intrinsic paramagnets include some transition metal ions, such as Fe³⁺ and Cr³⁺, and free radicals.

Examples of Intrinsic Paramagnetic Materials are Iron(III) Ion, Chromium(III) Ion, Oxygen Molecule.

Extrinsic Paramagnets

Extrinsic Paramagnetic Materials acquire paramagnetic properties due to impurities or defects in non-magnetic materials. Impurities introduce unpaired electrons into the material, causing paramagnetic behavior.

Examples include Ruby (Aluminum Oxide with Chromium Impurities), Copper Sulfate (CuSO4) with Unpaired Electrons, Doped Silicon with Phosphorus Impurities.

Application of Paramagnetic Materials

Various properties of Paramagnetic materials are,

• MRI (Magnetic Resonance Imaging): Paramagnetic contrast agents are used to increase the visibility of certain tissues or structures in MRI. These contrast agents contain paramagnetic ions such as gadolinium, which help improve the contrast between different tissues in the body.
• Electromagnetic Devices: Paramagnetic materials are used in the construction of many electronic devices, including inductors and transformers.
• Research and Analysis: Paramagnetic materials are used for various research and analysis in the laboratory. For example, paramagnetic ions can be used as probes in spectroscopy and other analyzes to study the structure and properties of different substances.
• Magnetic Bearings: In some applications, magnetic bearings that take advantage of the magnetic properties of the materials can operate. These bearings can provide a non-contact, low-friction way to support rotating parts, reduce wear and improve the quality of rotating machinery.
• Magnetic Separation: Magnetic materials can be separated from non-magnetic materials using magnetic separation technology. This is particularly useful in industries such as mining.
• Nuclear Magnetic Resonance (NMR) Spectroscopy: Paramagnetic ions can affect NMR signals in NMR spectroscopy. Scientists use paramagnetic materials to study local regions and molecular interactions, providing valuable information in fields such as chemistry and biochemistry.

Paramagnetic, Diamagnetic and Ferromgnetic Material

There are three kinds of magnetic material namely Paramagnetic, Diamagnetic and Ferromagnetic Material. A detailed comparison between them is tabulated below:

Difference Between Paramagnetic, Diamagnetic and Ferromagnetic Material
Property	Paramagnetic Materials	Ferromagnetic Materials	Diamagnetic Materials
Behavior	Weakly attracted to external magnetic fields.	Strongly attracted to external magnetic fields, and can retain magnetization.	Weakly repelled by external magnetic fields.
Magnetic Moment	Alignment of magnetic moments with the applied field is temporary.	Spontaneous alignment of magnetic moments, leading to strong and persistent magnetization.	Alignment of magnetic moments opposite to the applied field is weak and temporary.
Origin of Magnetism	Due to unpaired electrons in the presence of an external magnetic field.	Arises from the alignment of atomic magnetic moments, which can persist even in the absence of an external field.	Induced by an external magnetic field; all electrons are paired.
Materials Examples	Iron, Aluminum, Platinum, Gadolinium.	Iron, Cobalt, Nickel.	Copper, Bismuth, Zinc.
Magnetic Susceptibility	Positive	High positive magnetic susceptibility.	Negative
Curie Temperature	Typically, there is no Curie temperature	Above the Curie temperature, ferromagnetic materials lose their magnetic properties.	Below the Curie temperature, diamagnetic materials exhibit weak repulsion.
Applications	MRI contrast agents, electromagnetic devices, research probes.	Permanent magnets, transformer cores, magnetic storage media.	Magnetic levitation, superconductors, screening of magnetic fields.
Interaction Range	Interaction is short-range and weak.	Interaction can extend over longer distances.	Interaction is weak and short-range.

Formulas related to Paramagnetic Materials

There are two formulas related to properties of Paramagnetic Material which are mentioned below:

• Magnetic Susceptibility
• Curie Law

Let's discuss these two formulas in detail

Magnetic Susceptibility (χ) for Paramagnetic Material

Magnetic susceptibility of an object, expressed as χ, measures its response to an external magnetic field. For paramagnetic materials, the magnetic susceptibility is positive and small. The formula is:

χ = M/H

where,

• χ is Magnetic Susceptibility
• M is Magnetization
• H is applied Magnetic Field

Example: Suppose you have a paramagnetic material that has a Magnetization of (M) of 2.5 A/m when exposed to a magnetic field (H) of 500 A/m. Calculate the magnetic susceptibility.

χ = M/H

χ = 2.5/500

χ = 0.005

Curie's Law for Paramagnetic Material

Curie's law describes the magnetic susceptibility of paramagnetic materials as a function of temperature. The formula is given by:

χ = C/T

where

• χ is Magnetization
• C is the Curie constant
• T is the absolute temperature.

Example: Consider a paramagnetic material with a Curie constant (C) of 2.0 1.3047 KATm . Calculate the magnetic susceptibility at an absolute temperature (T) of 300K using Curie's law

χ = C/T

χ = 2.0/300

χ = 0.0067

Also, Check

• What is Magnet?
• Magnetization and Magnetic Intensity
• Diamagnetic Materials
• Ferromagnetic Materials