Magnetic coercivity is a measure of the resistance of a material to becoming demagnetized when exposed to an external magnetic field. It is the amount of magnetic field strength required to reduce the magnetization of a material to zero.
The Units Of Coercivity
Coercivity, also known as a magnetic coercive force, is typically measured in units of amperes per meter (A/m) or oersteds (Oe)
In the International System of Units (SI), coercivity is typically measured in units of amperes per meter (A/m). In contrast, in the centimeter-gram-second (cgs) system, it is commonly measured in units of oersteds (Oe). The prefix “kilo” (k) is used to indicate a multiple of 1000, so “kA/m” and “kOe” refer to 1000 amperes per meter and 1000 oersteds, respectively.
The Difference Between Hcb And Hcj
There are two different kinds of Coercivity: Hcb and Hcj.
Hcb, or normal coercivity, refers to the external magnetic field needed to reduce the magnetization of a material to zero. This measures the material’s resistance to becoming demagnetized when subjected to an external magnetic field.
Hcj, or intrinsic coercivity, refers to the internal magnetic field needed to reduce the magnetization of a material to zero. This measures the material’s inherent resistance to becoming demagnetized without the influence of external magnetic fields.
High Coercivity In Hard Magnetic Materials
One advantage of high coercivity in hard magnetic materials is their permanent magnetization. This means that they retain their magnetization even without an external magnetic field once they are magnetized. This makes them useful in applications where a permanent magnet is required, such as in magnets for loudspeakers and microphones or in magnetic separators used in mining and recycling.
Another advantage of high coercivity in hard magnetic materials is their high energy product. The energy product measures the magnetic field strength and density that a material can support. Materials with a high-energy product can generate a strong magnetic field, making them suitable for use in applications such as motors and generators.
In addition, high coercivity in hard magnetic materials makes them more resistant to external magnetic fields. This is because they require a strong magnetic field to be demagnetized, which means that they are less susceptible to the effects of external magnetic fields, such as those generated by electrical currents. This makes them more stable and reliable in applications where they may be exposed to such fields.
Low Coercivity In Soft Magnetic Materials
One advantage of low coercivity in soft magnetic materials is that they can be easily magnetized and demagnetized. This makes them useful in applications where the magnetization of the material needs to be easily controlled, such as in electrical transformers and motors. In these applications, the magnetization of the material can be easily changed by applying a small magnetic field, which allows the transformer or motor to operate efficiently.
Another advantage of low coercivity in soft magnetic materials is their low hysteresis loss. Hysteresis loss is the energy loss that occurs when the magnetization of a material is changed. Materials with low hysteresis loss have low energy loss during magnetization and demagnetization, which makes them more efficient in electrical applications.
In addition, low coercivity in soft magnetic materials makes them more resistant to magnetic field disturbances. This is because they can quickly adjust their magnetization to changes in the external magnetic field. This makes them less susceptible to the effects of external magnetic fields, such as those generated by electrical currents, which can interfere with the operation of electrical devices.
What Factors Will Affect The Magnetic Coercivity
Several factors determine the magnetic coercivity of a material:
- Material type and purity: The type and purity of the material play a crucial role in determining its magnetic coercivity. Materials with a higher degree of purity and uniformity tend to have higher magnetic coercivity than impure or heterogeneous materials.
- Applied magnetic field strength: The strength of the magnetic field applied to a material can significantly impact its magnetic coercivity. Materials with higher magnetic coercivity can withstand stronger applied magnetic fields without becoming demagnetized.
- Material temperature: The temperature of a material can also affect its magnetic coercivity. Materials with higher magnetic coercivity tend to have higher Curie temperatures, the temperature at which the material loses its magnetic properties.
- The presence of impurities or defects in the material: The presence of impurities or defects in a material can have a negative impact on its magnetic coercivity. These impurities and defects can act as sites where the magnetic field can be easily reversed, making the material more susceptible to demagnetized.
- The amount of stress on the material: The amount of stress on a material can also affect its magnetic coercivity. Materials that are under high levels of stress tend to have lower magnetic coercivity than materials that are not subjected to stress.
- The presence of any magnetic anisotropy: Magnetic anisotropy is the property of a material that allows it to have different magnetic properties in different directions. Materials with high levels of magnetic anisotropy tend to have higher magnetic coercivity than materials with low levels of magnetic anisotropy.
How To Measure Magnetic Coercivity?
There are several methods for measuring the magnetic coercivity of a material.
One method is the vibrating sample magnetometer (VSM) method. In this method, a small material sample is placed in a magnetic field, and the field strength is gradually increased. The sample’s magnetization is measured as the field strength increases, and the field strength at which the sample’s magnetization is reduced to zero is recorded as the material’s coercivity.
Another method for measuring magnetic coercivity is the SQUID (Superconducting Quantum Interference Device) method. In this method, a small material sample is placed in a magnetic field, and the sample’s magnetization is measured as the field strength is varied. The field strength at which the sample’s magnetization is reduced to zero is recorded as the material’s coercivity.
Other methods for measuring magnetic coercivity include the Hall effect method, the Barkhausen noise method, and the loop tracer method. These methods all involve measuring the magnetization of a material as the external magnetic field is varied and recording the field strength at which the material’s magnetization is reduced to zero as the material’s coercivity.
Coercivity And Hysteresis Loop
The shape of the hysteresis loop is determined by the material’s magnetic properties, such as its coercivity and permeability. In general, materials with high coercivity have a narrow hysteresis loop. This means that the material’s magnetization changes relatively little in response to changes in the external magnetic field. In contrast, materials with low coercivity have a wide hysteresis loop, which means that their magnetization changes significantly in response to changes in the external magnetic field.
The coercivity of material also affects the area enclosed by the hysteresis loop. Materials with high coercivity have a smaller hysteresis loop area, meaning they have low hysteresis loss. This means they have low energy loss during magnetization and demagnetization, making them more efficient in electrical applications. In contrast, materials with low coercivity have a larger hysteresis loop area, meaning they have high hysteresis loss. This makes them less efficient in electrical applications.
The Significance of Coercivity
Coercivity is an important property of magnetic materials and has many practical applications. Materials with high coercivity are more resistant to losing their magnetic properties, making them useful in various applications.
One common use for materials with high coercivity is in producing permanent magnets. These magnets are made from materials with a strong, stable magnetic field. They are used in various applications, from electric motors and generators to loudspeakers and MRI machines.
In addition to its use in permanent magnets, coercivity is also essential in producing magnetic recording media, such as hard disks and tapes. Materials with high coercivity can maintain a stable magnetic field, which allows them to store large amounts of data for long periods without losing their magnetic properties.
Furthermore, coercivity is also an essential factor in the design of magnetic sensors, such as those used in electronic compasses and other navigation systems. These sensors rely on the stability of magnetic fields to accurately measure magnetic fields and detect orientation changes.
Conclusion
Learning more about magnetic coercivity can help us understand the behavior of magnetic materials and optimize their performance in various applications ranging from consumer electronics to medical equipment.
By understanding the principles of coercivity, you can make better choices when selecting materials for magnetic applications. Additionally, knowing how coercivity affects energy loss and hysteresis can help you maximize the efficiency of your designs.
For more information about magnetic coercivity, contact a specialist at JdaMagnet today!
