This book provides a comprehensive review of thin film magnetoresistive (MR) sensors, including the theory of magnetoresistive effects as well as the design, fabrication, properties and applications of MR sensors. It is mainly addressed to potential and actual users of these sensors, giving essential information about the performance of various kinds of sensors, including Permalloy magnetoresistors, spin valve sensors, multilayer sensors, colossal effect sensors, spin dependent tunnelling sensors and magnetoimpedance sensors. It will also be of use to the specialist currently employing these sensors. With over one thousand references it provides a fully referenced and up-to-date review of theory, development and use to date. The book is divided into three independent parts. Part one is concerned with the most widely used sensors-anisotropic magnetoresistive sensors (AMR). The second part is devoted to new giant magnetoresistive (GMR) sensors and those still in development, whilst the third part describes the applications of MR sensors, especially in data storage systems, industrial measurements and non-destructive material testing systems.