A magnetic head slider assembly having an air bearing surface (10) to enable the sliderto float relative to a surface of a rotating magnetic disk and provided with a thin-film magnetic head element is formed of a composition comprising zirconium oxide. The composition can further comprise yttrium oxide in an amount in the range of 6 to 11 mol %, and preferably 8 to 10 mol %, the magnetic head slider having structural stability and superior machining prosperities.