Engineering Physics

7.9 Anti-ferromagnetic substances

Anti-ferromagnetism arises when the spin magnetic moments of neighbouring atoms of the crystal are anti-parallel so that the spin magnetic moments of alternate atoms are parallel. Because of opposite spin moments, we consider an anti-ferromagnetic crystal consists of two different types of atoms i.e., say A-type atoms and B-type atoms. T he crystal structure consists of interpenetration of two cubic sublattices, one of with A atoms and the other with B atoms. One sub-lattice spontaneously magnetized in one direction and the other in opposite direction. One may therefore suggests the BCC structure for an anti-ferromagnetic crystal with A atoms occupying the corner points and B atoms at the centre of the cubes ...