Chapter 2 - Magnetotransport Properties of Ultrathin Metallic Multilayers: Microstructural Modifications Leading to Sensor Applications

Abstract

This chapter delineates magnetotransport properties of ultrathin metallic multilayers. In man-made devices, where the information is transmitted and processed in electrical form through the transport of electrons, a sensor is defined as “a device that receives a signal or a stimulus and responds with an electrical signal.” The stimulus is the quantity, physical property, or condition that is sensed as an input signal. Thus, a sensor responds to the stimulus and converts it into an electrical signal, which is compatible with electronic circuits. The sensor's output signal may be in a form of voltage, current, or charge. An ideal or theoretical output-stimulus relationship exists for every sensor that is characterized by the so-called transfer function. Moreover, a related technology, giant magnetoresistive (GMR) sensing can provide much more sensitivity for a given size head. GMR is the change of resistance when the magnetic alignment of adjacent ferromagnetic (FM) layers separated by nonmagnetic material (NM), called “spacer,” is changed. Finally, it has been argued that an MR sensor using these techniques would have some advantages over previous designs—including small size, power needs, and implementation of a single excitation stripe for both excitation and feedback biasing.