Magnetization & H, B Relation

Magnetization M is the magnetic moment per unit volume of a material: M = m/V. Units: A/m.

When a material is placed in an external field H, it develops a magnetization that adds to the total field: B = μ₀(H + M).

For LINEAR materials: M = χ·H, where χ is the magnetic susceptibility (dimensionless).

Permeability: μ = μ₀(1 + χ) = μ₀·μ_r, where μ_r is the relative permeability.

Three classes: diamagnetic (χ < 0, very small, μ_r ≈ 1), paramagnetic (χ > 0, small, μ_r ≈ 1), ferromagnetic (χ ≫ 1, very large, nonlinear).

H is determined by free currents alone; B includes contributions from magnetization.

In free space M = 0 ⇒ B = μ₀H.

Magnetization saturates in ferromagnets at high H — all spins aligned, can't increase M further.