Effective-refractive-index method for a flying-height sensor using frustrated total reflection and its application to flying-height measurement on anactual magnetic disk

It is necessary to measure the flying height of a slider on an actual magne tic disk when designing magnetic disk drives. However in typical methods fo r measuring spacing, the magnetic disk is usually replaced with a glass dis k, To measure this real spacing, we developed a flying-height sensor based on frustrated total reflection. However, to measure the real flying height optically, the phase shift on reflection at a magnetic disk is an important problem. We developed a theoretical treatment of this problem and introduc ed the modified effective-refractive-index method. We measured the effectiv e-refractive-index of an actual magnetic disk. Flying height on the magneti c disk was also measured by using the obtained effective-refractive-index. This result was compared with the flying heights measured by using the trad itional interference method. Both measurements agreed well with an error of less than 2 nm.