This course provides a comprehensive introduction to the use of materials in contributing to the quality and continuing development of our society and environment. The crystal structures of technologically important materials will be described; principles and applications of x-ray and neutron diffraction in determining crystal and magnetic structures; summary of the various types of structural states (such as polycrystalline, nanostructured, amorphous); phase diagrams relating to microstructure and mechanical properties; origins of different types of magnetic behaviour and properties of magnetic materials; basic theories of diamagnetism, paramagnetism and ferromagnetism. The applications of magnetic materials - their use in permanent magnets, transformers and information storage - magnetic disks and tapes and magneto-optical data storage.