Magnetic materials are the chief ingredients and key components for many technological marvels. The key factors deciding upon their effectiveness are often considered remanence (Br), coercivity (Hcb and Hcj), and energy product (BHmax). These parameters interlink not only the basic features of the material but also its performance in the industry. Let's have a closer look at what these parameters are and how they relate to everyday design.

Remanence (Br)

Remanence means the B field level a material conserves even after the external magnetic field is absent. Its physical significance indicates how well a material holds its magnetic energy. Remanence is the initial point of the magnetization curve (B value at H=0), and a considerable Br value suggests that the material can offer a larger static magnetic field. For instance, the remanence of neodymium iron boron (NdFeB) typically ranges from 1.0 to 1.4 Tesla (T), suitable for high-magnetic-field applications like permanent magnet motors. The Br of TOPMAG's NdFeB N52 series stands out at 1.48T.

Coercivity (Hcb and Hcj)

Coercivity finds its magnetic split in the magnetic coercivity (Hcb) and intrinsic coercivity (Hcj) that measure, in turn, the material's resistance to the external demagnetizing fields and the difficulty of the magnetic domain reversal, as we know. Hcb refers to the strength of a magnetic field required to decrease the magnetic flux density (B) to zero of the substance, a process called demagnetization, and Hcj refers to the strength of a magnetic field required to reduce the magnetization (M) to zero, i.e., the material's ability to resist the demagnetization process carried out by an external field. The crucial difference between Hcb and Hcj is that Hcb deals with the lead-in-location effect, while Hcj describes the lead-out-location effect (a problem of magnetocrystalline anisotropy). The material becomes irrevocably demagnetized if the reverse magnetic field strength surpasses Hcj.

Energy Product (BHmax)

The maximum energy product (BHmax) is the value at which the B×H product on the demagnetization curve is the largest, and the product has virtue from the engineering point of view because it reveals the magnet's volumetric efficiency. For example, NdFeB can obtain a BHmax of 400 kJ/m³ (≈50 MGOe), highly suitable for use in compact applications such as micro-motors. The demagnetization curve is in the second quadrant of the B-H plane (H is negative, B is positive), and the actual operating point can be found by the intersection of the load line (the one defined by the magnetic circuit air gap and material properties) and the demagnetization curve.