Yasuko Teragaki

Thermal stability of Pt/Co multilayered films

The thermal stability of Pt/Co multilayered films with various underlayers has been studied by annealing up to 400 °C. In Pt/Co films sputtered on glass or amorphous AlN underlayers, their coercivity and the squareness of magnetic hysteresis loops are degraded by annealing above 300 °C. In contrast, in films sputtered on ZnO or Pt underlayers, the coercivity is remarkably increased by annealing at 300 °C. The film with the ZnO underlayer shows a hysteresis loop with perfect squareness even after annealing at 400 °C. The results of x‐ray diffraction indicate that the ZnO underlayer not only enhances the fcc Pt/Co(111) orientation but also prevents the decay of the multilayered structure during annealing. The results of laser microannealing using a conventional disk drive system also indicate that the Pt/Co films with ZnO underlayers have superior resistance to laser damage.

Microstructures of Pt/Co Films Deposited on Sputter-Etched Underlayers

Pt/Co multilayered films deposited on a sputter-etched SiN underlayer show larger magnetic anisotropy (1×106 erg/cm3) and better squareness(=1) than those on nonetched underlayers. The results of small-angle X-ray diffraction indicate the improvement of the multilayer structural order due to the etching. According to the transmission electron microscopy observation and the electrical resistivity measurement, the etching of underlayers transforms the Pt/Co films from island structure to continuous structure in an early stage of film growth. The scanning tunneling microscopy observation suggests that the sputter etching flattens the surface of the underlayer.

Magnetic field modulation recording on Pt/Co magneto-optical disks

Recording properties have been investigated for a magnetooptical disk made of Pt/Co multilayers. The disk exhibits good recording properties for both light intensity modulation and field modulation methods. Reasonable recording properties, namely a carrier-to-noise ratio (CNR) of 46 dB and a block error rate of 1.9%, have been obtained for the field modulation method which seems to satisfy usual standards. However, in the case of low modulation fields, the Pt/Co disk exhibits lower CNR than conventional disks made of rare earth-transition metal amorphous films because of lower recording carrier. >

Structure and recording properties of Pt/Co magneto-optical disks with various underlayers

Abstract Structure and recording properties of Pt/Co magneto-optical disks prepared on ZnO, AIN and SiN underlayers are reported. The disk with SiN has very flat surface, but shows lower magneticanisotropy and smaller coercivity, which results in higher writing noise. The disk with ZnO shows higher magnetic anisotropy, but higher initial noise because of the lower surface flatness.