Question

A domain in ferromagnetic

iron is in the form of cube of side 1 µm. Estimate the number of iron atoms in the domain, maximum possible dipole moment and magnetisation of the domain. The molecular mass of iron is 55 g/mole and

density is 7.9 g/cm3Assume that each iron atom has a dipole moment of 9.27 × 10-24

Am2.​

Answer 1

.$\bf\large\underline\green{Answer:-}$

Solution: The volume of the cubic domain

V = (10-6)3

= 10-18 m3

= 10-12 cm3

mass = volume × density = 7.9 × 10-12 g.

An Avogadro number (6.023 x 1023) of iron

atoms has mass 55 g.

The number of atoms in the domain N

The maximum possible dipole moment mmax

is achieved for the case when all the atomic

moments are perfectly aligned (though this

will not be possible in reality).

mmax = 8.65 × 1010 × 9.27 × 10-24

= 8 × 10-13 Am2

Magnetisation M = mmax / domain volume

= 8 × 105Am-1