Coercivity

Coercivity is the concept where we can completely understand the stability and durability of a magnetic material. In the concept of magnetic hysteresis, coercivity plays a major role. Coercivity shows the relationship between magnetization and magnetic field. In the hysteresis loop, the magnetization will reduce to zero whenever the opposite magnetic field is applied. This article will briefly discuss the coercivity concept, its applications, advantages, and disadvantages.

What is Coercivity?

The magnetic field needed to demagnetize the magnetic material completely is known as coercivity. The coercivity can be well used in permanent magnets to determine the withstand strength of the magnetic material. If we take a solenoid as an example, if we increase the current through the solenoid, the magnetizing force also increases. This behavior represents the alignment of ferromagnetic material until no further increase in current is possible. Thus, there is no use for an increase in the current of the solenoid.

Now we decrease the solenoid current; hence, the magnetic intensity will reduce to zero. Next, the current in the solenoid is reversed and increased slowly. Certain domains are flipped until the net magnetic field is reduced to zero. It means that to reduce the retentivity to zero, we need to apply a magnetizing force in the opposite direction. The value of magnetizing force is called the coercivity of the material.

Coercivity is a fundamental property in the field of magnetism. Coercivity can withstand demagnetization. This feature is important in ferromagnetic materials, which work on spontaneous magnetization and serve as major components in various applications. Coercivity is the strength of a material that opposes the magnetic field to reduce its magnetization to zero.

Magnetic Material and Coercivity

The magnetic material and coercivity is described in the following terms:

• Relationship with Ferromagnetic Material
• Relationship with Magnetic Hysteresis

Coercivity

Relationship with Ferromagnetic Material

Also referred to as “magnetic memory,” another very important property of ferromagnetic materials is magnetic coercivity. Emerging from their ferromagnetic property, these materials like iron and its alloy. On the other side in case the material is in the magnetic state, the coercivity allows the determining of the resistance to the demagnetization of that material.

These materials learn their magnetic properties only if the external magnetic field or the heat is present in the environment. The magnetizing ability and also the perfect alignment of spins within the tripodal magnets can be used to the full advantage of the permanent magnets and the magnetic storage devices.

The coercivity of the ferromagnetic allows us to read the state of the magnetic material by affecting the direction to the magnetized. In an attempt to turn away the demagnetizing forces, the coercivity may also turn out to be the factor responsible for the much higher magnetization. By using this property in your system components, you can accomplish the permanent magnet function.

Relationship with Magnetic Hysteresis

The ability of ferromagnetic materials to be exposed to different electrical fields and exhibit the magnetic hysteresis property is the most essential feature of ferromagnetic materials. The lagging magnetization in the magnetic domain related to the variation of the magnetic field is illustrated. The coercive nature of magnetism has a very profound impact on the form of the magnetization hysteresis curve. In figuring out the point of magnetization which starts to flip direction, we ought to use the coefficient.

A greater level of coercivity will result in a broad hysteresis loop – which means that the material would need a very significant amount of energy to be demagnetized and then re-magnetized. These properties are for instance applied in power applications such as transformers and inductors. In magnetic materials engineering for a range of applications, the link between the coercivity and magnetic hysteresis is an essential result.

Types of Coercivity

These are of two types: intrinsic coercivity and extrinsic coercivity. It can be more useful in the design of permanent magnets, magnetic recording media, and various electronic devices. Coercivity can also increase the reliability and efficiency of various industries. So There are two types of coercivity:

• Intrinsic coercivity
• Extrinsic coercivity

Intrinsic coercivity

Intrinsic coercivity is a magnetic property that characterizes the ability of a ferromagnetic material to resist demagnetization. It represents the strength of a magnetic field required to demagnetize a magnetic material to zero. After it magnetized in a specific direction.

Large coercive force

Materials with high intrinsic coercivity are more resistant to demagnetization. In permanent magnets, stable magnetization is essential, so these properties are well-suited to applications like permanent magnets, magnetic recording devices, etc. It is measured in amperes per meter (A/m). Intrinsic coercivity is crucial while designing magnetic materials for various applications like data storage applications, magnetic sensors, and electric motors.

Extrinsic Coercivity

Extrinsic coercivity is a magnetic property that represents the resistance of a ferromagnetic material to demagnetization when an external magnetic field is applied. Various factors, such as shape, size, and the presence of defects, determine extrinsic coercivity.

Materials with high extrinsic coercivity require a stronger magnetic field to fully demagnetize them. This property is more useful for stable magnetization in applications like permanent magnets and magnetic recording devices. The extrinsic coercivity of a material can be optimized by some techniques, such as kneeling, alloying, or adding impurities. Extrinsic coercivity is essential in designing applications such as magnetic data storage, sensors, and magnetic resonance imaging (MRI) devices.

Small coercive force

Factors Affecting Coercivity

• Shape and size­: The form and size of magnets can change­ their coercivity. Smaller particle­s, due to more surface space­s and less flexible walls, have­ more coercivity.
• Tempe­rature: It too can change coercivity. Whe­n temperature rise­s and falls, the magnetic material’s coe­rcivity can shift.
• Defects and impurities: Magne­tic materials, if they have proble­ms like dislocations or impurities. It can produce diffe­rent magnetic reactions. The­se then can alter coe­rcivity.
• Mechanical stress: It too can switch the magne­tic features of a substance, affe­cting its coercivity.

Advantages

• Stable: High-coercivity materials are stable. It does not undergo any changes.
• Energy-efficient: They are energy-efficient. This property is more suitable for applications like electric motors and some industrial applications.
• Durability: It can withstand different temperatures because the material is designed to work at high temperatures.
• Modified easily: These materials can easily be modified in different ways based on our usage.
• Reliable performance: The performance is good as compared to other types, and these materials can perform well in all conditions.

Disadvantages

• Availability: The resources available are less and more challenging, too. The extraction and recycling are also difficult.
• Choice is limited: All the materials for designing permanent magnets are not used for high coercivity, so the choice of materials is limited.
• Hysteresis loss: Hysteresis loss can be identified in electric transformers. Where these hysteresis losses are more caused by this property, they can lead to a reduction in efficiency.
• Brittleness: Brittleness is also a big disadvantage. Because of this, the material can easily break and crack.
• High cost: some of the coercivity materials are expensive, so the cost of the system will increase.

Applications

• Permanent magnets: This property is used mostly in the design of permanent magnets.
• Security systems: In security systems like CC TVs, sensor coercivity is used.
• Medical applications: In medical applications like magnetic resonance imaging, MRI
• Recording devices: These can be used in magnetic recording devices.
• Sensors: This property can be highly useful in magnetic sensor applications.

Conclusion  

In conclusion, coercivity plays a major role in the study of magnetic properties. These can be used in the design of permanent magnets in industrial applications. In this article, we discussed the types, applications, factors affecting, and pros and cons of coercivity properties. Intrinsic and extrinsic coercivity can be used in a variety of systems based on their applications.

Some of the factors that affect this property are temperature, heat treatment, alloying, etc. Before designing permanent magnets, be well-known about the property. Research is going on to develop the new features and design of the permanent magnets. Engineers are studying more about the coercivity property.

FAQs on Coercivity

Why is coercivity important in magnetic recording media?

Coercivity can maintain stable data. It prevents the accidental erasing and corruption of the media that stored on a hard disc drive (HDD).

Is coercivity reversible or irreversible? 

Coercivity is reversible when a material magnetization can reduced to zero. It can restored by applying an external magnetic field in the opposite direction.

What are the consequences of low coercivity in magnetic materials?

Low coercivity can lead to unidirectional demagnetization. It can also affect the performance of the device and impact the efficiency of the system.