The demand for high capacity storage of information and sharing of data has been the major driving force behind the fast development in the electronic storage industry. The price per gigabyte and the size of hard disk drives (HDD) have been steadily decreasing since the late 1980s. Recently, IBM has announced their record-breaking 16.8 gigabyte hard disk drive which is based on a new read-head design. The new design was possible due to a discovery in 1988 of a new phenomenon called the "giant magnetoresistive (GMR)" effect. The discovery was made by two scientists: Peter Gruenberg of KFA research center in Jülich, Germany, and Albert Fert of the University of Paris-Sud. Independently, they demonstrated that the resistance of a multilayer thin film comprised of ferromagnetic layers sandwiching a conducting layer can change between 6% to 50% depending on the direction of an external magnetic field. The layers are very thin ranging from 0.1 to 10 nm. However, the initial demonstration was made using single crystal metal layers grown by techniques that are not easily compliant with mass production. IBM researchers have reproduced the results using a deposition method called sputtering which made the production of GMR sensors economical and compatible with higher volume production.

In this project, we have fabricated GMR sensors using electron beam evaporation. The latter method can produce materials with high purity compared to sputtering while it is also compatible with mass production. The sensors consist of 30 nm of nickel oxide (antiferromagnetic layer), 10 nm of permalloy (magnetic layer), 2 nm of copper (conductive layer), and 10 nm of permalloy (magnetic layer) deposited on a silicon wafer. The total thickness is less than 55 nm.