Simulation parameters

  The microstructure of the magnets is modeled by hexahedrons of $20 \times 20 \times 80$ nm size representing magnetic particles. A single particle consists of 16 grains, which are cubes of 10 nm edge length. Two phases have been considered: A hard magnetic Nd₂Fe₁₄B rich phase (red cubes) and a soft magnetic phase of Fe₃B(blue). The material parameters are given in table 3. The grains have been arranged in a checkerboard like pattern.

 

 

Parameter Nd₂Fe₁₄B Fe₃B

Exchange constant A [J/m] 1.25e-11 1.25e-11

Saturation polarisation J_s [T] 1.61 1.615

Type of anisotropy easy axis easy plane

Anisotropy constant K₁ [J/m³] 4500000 322000

Anisotropy constant K₂ [J/m³] 660000

$$l_{ex}=\sqrt{A/K_1}$$ 1.6 6.23