If a number of electrons in a unit volume of the material have a total orbital angular momentum of J o with respect to a certain axis, their magnetic moments would produce the magnetization of M o = e / 2 m ⋅ ⋅ J o . For the spin contribution the relation would be M s ≈ ≈ e / m ⋅ ⋅ J s . A change in magnetization, Δ Δ M , implies a proportional change in the angular momentum, Δ Δ J ∝ ∝ Δ Δ M , of the electrons involved. Provided that there is no external torque along the magnetization axis applied to the body in the process, the rest of the body (practically all its mass) should acquire an angular momentum − − Δ Δ J due to the law of conservation of angular momentum.