Perpendicular Magnetic Recording Media on Various Hard-Disk Substrates
Co-Cr perpendicular media on rigid substrates were studied. We used untextured glass substrates for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard disk media deposited onto different substrates: untextured glass, silicon single crystal, chemically textured alumite, and Mn-Zn ferrite. We compared these substrates with respect to their crystallographic properties, head-to-medium spacing, and record/playback characteristics.
Structures and magnetocrystalline anisotropy of single crystal permalloy films deposited by sputtering method.
Single crystal Permalloy films were grown epitaxially on (001) GaAs substrates by sputtering method. The relationship between crystal orientations for Permalloy and GaAs are (001)NiFe//(001) GaAs, NiFe// GaAs. The crystal structures of Permalloy films are deformed from cubic to tetragonal. The films of positive and negative tetragonal strain have small and large unit cell volume, respectively. The films with small lattice constant in the film plane have large strain distribution. The magnetocrystalline anisotropy for the films of large strain distribution is small, and that for films of negative tetragonal strain is large.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.