Question

At saturation, when nearly all the atoms have their magnetic moments aligned, the magnetic field is equal to the permeability constant ?0 multiplied by the magnetic moment per unit volume. In a sample of iron, where the number density of atoms is approximately 8.50 1028 atoms/m3, the magnetic field can reach 2.00 T. If each electron contributes a magnetic moment of 9.27 10-24 A · m2 (1 Bohr magneton), how many electrons per atom contribute to the saturated field of iron? electrons/atom

Answer 1

Number of atoms N = 8.50 x 10²⁸ /m³

magnetic field B = 2T

magnetic moment M = 9.27 x 10^-24 A-m²

B = ₀M n

hence number of electrons n = B/ ₀M

= 2/ (4pi. x 10^-7 x 9.27 x 10^-24)

= 17.2 x 10²⁸ /m³

now n/N = 17.2 x 10²⁸ /m³ /   8.50 x 10²⁸ /m³

= 2 electrons / atom