Define the following terms:

a) Primitive unit cells

b) Schottky defect

c) Ferromagnetism

a) Primitive unit cells–it is defined as a unit cell in which the atoms are present at the corners of the cube. 1/8 is contributed per corner atom of the cube.

b) Schottky defect - It is defined as vacancy defect which is shown by ionic solids. In this defect, an equal number of cations and anions are missing thereby maintains the electrical neutrality which decreases the density of the substance. For example – NaCl and AgBr.

c) Ferromagnetism – It is defined as the property of a substance by which when it is placed in a magnetic field it gets strongly magnetised in the direction of the field. Examples – Fe and Ni.