High - performance NdFeB magnets are characterized by a set of technical parameters that define their magnetic capabilities and suitability for different applications.

Magnetic Remanence (Br)

Magnetic remanence, denoted as Br, is a measure of the magnetic flux density remaining in the magnet after the external magnetic field has been removed. In high - performance NdFeB magnets, the remanence can be quite high. For example, in some top - grade sintered NdFeB magnets, the remanence can reach up to 1.45 T. A higher remanence value indicates a stronger residual magnetic field in the magnet. This is crucial in applications such as electric motors, where a strong magnetic field from the permanent magnet is required to interact with the magnetic field generated by the motor's coils to produce torque. In a brushless DC motor used in an electric vehicle, a high - remanence NdFeB magnet in the rotor can enhance the motor's power output and efficiency.

Intrinsic Coercive Force (Hcj)

The intrinsic coercive force, Hcj, represents the ability of the magnet to resist demagnetization. High - performance NdFeB magnets can have an intrinsic coercive force of up to 2786 kA/m. This high value ensures that the magnet retains its magnetic properties even when exposed to external magnetic fields or other factors that could potentially cause demagnetization. In aerospace applications, where the magnets may be subjected to varying magnetic fields during flight, a high Hcj is essential. For instance, in the magnetic sensors used for navigation in an aircraft, the NdFeB magnets need to maintain their magnetic orientation precisely, and a high intrinsic coercive force helps in achieving this stability.

Magnetic Energy Product (BH)max

The magnetic energy product, (BH)max, is a key parameter that indicates the amount of magnetic energy stored in the magnet per unit volume. High - performance NdFeB magnets can have a (BH)max value that is significantly higher compared to other types of permanent magnets. As mentioned before, hot - pressed NdFeB magnet rings can have a maximum radial magnetic energy product in the range of 240 - 360 kJ/m³. A higher magnetic energy product means that the magnet can deliver more magnetic energy, which is beneficial in applications such as magnetic separators. In a mining operation, a magnetic separator with high - performance NdFeB magnets can more effectively separate magnetic minerals from non - magnetic ones due to the strong magnetic fields generated by the high - energy - product magnets.

Temperature Coefficients

The temperature coefficients of NdFeB magnets, including the temperature coefficient of remanence (αBr) and the temperature coefficient of coercivity (βHcj), are important parameters. The temperature coefficient of remanence typically ranges from - 0.100%/°C to - 0.085%/°C, and the temperature coefficient of coercivity ranges from - 0.64%/°C to - 0.41%/°C, depending on the magnet grade. These coefficients describe how the magnetic properties of the magnet change with temperature. In applications where the operating temperature can vary significantly, such as in industrial ovens or outdoor electrical equipment, knowledge of these temperature coefficients is crucial for predicting and compensating for any changes in the magnet's performance.