Tribo-mechanical characterization of thin film materials for magnetic recording

In the magnetic recording industry, the data storage density increases rapidly towards to a goal of 10 {dollar}rm GB/insp2{dollar} in the near future. To achieve this goal, a high reliability head/media interface is one of the keys to high density magnetic recording technologies. In this area, characterization of mechanical and tribological properties is an important aspect in development of high performance materials for tribological applications. The work in this dissertation consists of three sections: nano-mechanical characterization, nano/micro-tribological tests and thin film stress effects. In the first section, a comprehensive study on nano-mechanical properties of thin film materials is presented. The mechanical properties of thin films for recording heads, media and protective overcoats were characterized by nanoindentation. Hardness (H), elastic modulus (E) of these films are measured as a function of processing parameters. Strain rate sensitivities (m) of the ME tapes were found for different tape samples with different aging conditions. The second section is the primary focus of this dissertation. Tribological properties of thin film head materials and {dollar}rm TiBsb2{dollar} and {dollar}rm TiBsb2(N){dollar} overcoats were characterized using a sphere-on-flat wear tester developed in this work. Adhesion of SiC, C and CN ultra-thin (20 nm) overcoats was assessed by nanoscratch techniques. The most important work in this section is the development of a new technique for nanotribology using the depth sensing nanoindentation/nanoscratch instrument. This new technique is referred to as the depth sensing nanoindentation multiple sliding wear test. With this technique, a well defined critical sliding scan number and critical load can be determined for each ultra-thin overcoat depending on the loading modes (constant or ramped load) used. Another type of experiment conducted with this technique is fatigue wear tests, in which the normal load for indentation and sliding is controlled at a very low level so that the sample surface is not plastically deformed. Fatigue wear is observed for the ultra-thin SiC overcoat at a large sliding scan number. Very good repeatability and practicability of the new technique are demonstrated in this work. The last section focuses on stress effects on mechanical and tribological properties of thin films. A new method to control the stresses in thin films without changing other film properties such as microstructure is developed. Stress dependent behaviors of mechanical and tribological properties of thin films are described.