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HYSTERESIS Loop

Detailed Description of the BH Curve

The BH curve, also known as the hysteresis loop or demagnetization curve, is a graphical representation of the relationship between a permanent magnet’s magnetic field strength (H), measured in kiloOersteds (kOe), and its magnetic flux density (B), measured in kiloGauss (kGs). It illustrates how a magnet behaves under an applied external magnetic field, revealing critical magnetic characteristics such as remanence (Br), coercivity (Hc), intrinsic coercivity (Hci), and maximum energy product (BHmax). These properties determine the magnet’s performance in applications like badge magnets, motors, or sensors.

Key Features of the BH Curve:

  1. Remanence (Br): The magnetic flux density remaining in the magnet after the external magnetizing field is removed, indicating its residual strength (e.g., 14.8 kGs for N52 neodymium).
  2. Coercivity (Hc): The magnetic field strength required to reduce the magnet’s flux density to zero, showing resistance to demagnetization.
  3. Intrinsic Coercivity (Hci): The field strength needed to fully demagnetize the magnet, reflecting its ability to resist external magnetic fields.
  4. Maximum Energy Product (BHmax): The maximum energy a magnet can store, measured in Mega Gauss Oersteds (MGOe), indicating overall magnetic strength (e.g., 52 MGOe for N52 neodymium).
  5. Hysteresis Loop: The full BH curve traces the magnet’s magnetization cycle from saturation, through demagnetization, to reverse saturation, and back, forming a loop. The second quadrant (normal curve) is most relevant for practical applications, showing performance under typical operating conditions.
  6. Knee of the Curve: The point where the curve bends sharply, indicating the onset of significant demagnetization, critical for high-temperature or high-field applications.

Testing Process:

To generate a BH curve, a magnet sample (typically a small cube) is placed in a DC magnetizer between large pole pieces, creating a closed-loop system. The magnetizer applies a strong magnetic field to cycle the sample through:

  • Saturation: Full magnetization in one direction.
  • Demagnetization: Reducing the magnetic field to zero.
  • Reverse Saturation: Magnetizing in the opposite direction.
  • Return to Original Saturation: Completing the loop. This process plots B (flux density) against H (field strength), revealing the magnet’s behavior. Tests can be conducted at elevated temperatures to show how properties degrade, which is crucial for applications like badge magnets in varying environments.

Importance:

The BH curve is essential for engineers selecting magnets for specific applications. For example, badge magnets require high remanence and coercivity to hold securely without demagnetizing, while motors need high BHmax for efficiency. The curve’s shape varies by material (e.g., neodymium vs. ceramic), affecting suitability for different uses.

BH Curve for Neodymium N52 Magnet

Neodymium N52 magnets are among the strongest commercially available permanent magnets, with a maximum energy product of 50–53 MGOe and a remanence (Br) of ~14.8 kGs. Their BH curve shows a high, square loop, indicating strong magnetic performance and resistance to demagnetization at room temperature (~20°C). However, N52 magnets have a maximum working temperature of ~80°C, above which magnetic properties degrade, as shown in elevated-temperature BH curves.

BH Curve for Ceramic Magnet Grade 8

Ceramic (ferrite) Grade 8 magnets are widely used for their low cost and good demagnetization resistance, with a maximum energy product of ~3.5–4.0 MGOe and a remanence (Br) of ~3.9 kGs. Their BH curve is narrower than neodymium’s, reflecting lower magnetic strength but higher coercivity (Hc ~3.2 kOe), making them less prone to demagnetization. Ceramic magnets have a maximum working temperature of ~250–300°C, maintaining performance in higher-temperature environments compared to neodymium.

Comparison:

  • Strength: N52 neodymium has a much higher BHmax (50–53 MGOe vs. 3.5–4.0 MGOe) and Br (14.8 kGs vs. 3.9 kGs), making it far stronger for applications like badge magnets where secure holding is critical.
  • Temperature Stability: Ceramic Grade 8 outperforms N52 at higher temperatures (250–300°C vs. 80°C), with less degradation in magnetic properties, as shown by a more stable BH curve at elevated temperatures.
  • Hysteresis Loop: Neodymium’s square loop indicates high coercivity and efficiency, while ceramic’s narrower loop reflects moderate strength but robust demagnetization resistance.
  • Application Relevance: N52 is preferred for badge magnets (e.g., CMS Magnetics’ products) due to its strength, while Ceramic Grade 8 is better for cost-sensitive, high-temperature applications like motors or speakers.

Notes:

  • Data Source: The descriptions draw from web results (e.g.,,,,,) detailing BH curves, neodymium N52 properties (52 MGOe, 14.8 kGs Br), and ceramic magnet characteristics (3.5–4.0 MGOe, high coercivity).
  • Critical Consideration: BH curves vary by specific magnet composition and testing conditions. The provided values are typical but may differ slightly based on manufacturer or sample size. Always consult supplier data (e.g., CMS Magnetics) for precise curves.
  • Artifact IDs: The N52 artifact reuses the previous ID (7b1e1d01-8414-4e75-8b46-8295ac1c4cdb) as it extends the prior BH curve description, while the Ceramic Grade 8 artifact uses a new UUID (a2b3c4d5-9f10-4a12-9c78-123456789abc) for a distinct material.

If you need actual BH curve plots, further material comparisons, or specific data for other magnet grades, let me know, and I can refine the response or search for additional resources!