reduced the wavelength at which the polar Kerr tion process to produce the desired properties. rotation peaked by reducing the con- Platinum-cobalt alloys were also reported to centration in the . A reduction in platinum have potential as a future perpendicular record- concentration from 2 1 to 6 per cent resulted ing media by T. Hikosaka, T. Komai and Y. in the peak polar Kerr rotation moving hm633 Tanaka hmToshiba R & D. Center, Kawasaki, to 528 nm without any alteration in the peak who produced platinum-cobalt alloys with large polar Kerr rotation of 1.0'. Unfortunately this perpendicular anisotropies and coercivities by alloy did not possess magnetic properties suit- . able for magneto-optical storage applications. They obtained these properties by adding oxy- However it was suggested that perpendicular gen to the high pressure (30 mTorr) sputter- magnetisation could be induced in these alloys ing gas to produce a material in which the plat- by manufacturing samples having their c-axis inum-cobalt alloy grains were separated by perpendicular to the film plane, since in this amorphous boundaries. The oxygen rich material the direction of easy magnetisation is boundaries magnetically help to isolate the grain, along the c-axis. which produces the large perpendicular anisotropy and coercivity of the material. Perpendicular Recording Applications Conclusions The potential of palladidcobalt multilayers The results presented at this conference as a material for perpendicular magnetic mem- showed that both platinum- and -con- ory storage was demonstrated in a paper by B. taining materials have potential applications M. Lairson from Rice University, Texas, and as magnetic data storage materials, in both mag- J. Perez and C. Baldwin from Censtor neto-optical and perpendicular recording appli- Corporation, San Jose, California. They com- cations. The publication of the full conference pared palladiudcobalt multilayers with con- proceedings will be split between the Journal ventional cobalt- alloys and found of Applied Physics and the IEEE Transactions on that the palladidcobalt multilayers had a num- Magnetics later this year. J.M. ber of advantages, including the larger signal which is read back from the information stored References when using palladiudcobalt multilayers. The 1 S. Hashimoto, Y. Ochai and K. AsoJ ApPr Phys., multilayer properties of palladiudcobalt can 1990,67, (4), 2136 be easily modified to match a particular data 2 W. B. Zeper, F. J. A. M. Greidanus and P. F. Carcia, IEEE nuns. Mag., 1989,25, (3,3764 recording head, and the multilayers do not 3 H. Yamane, M. Kobayashi, N. Maeno and K. require the use of a high temperature deposi- Sato, Japanese Appl. 11274,039; 1989 Pretreatment of for Platinum Plating A variety of electrochemical processes make trosulphato platinous acid (DNS) system at pH use of platinum plated titanium electrodes. 2-3 (Met. Finish., 1994,92, (6), 85-87, 157). Before an adherent can be deposited Eight different etchant compositions were con- onto the titanium, however, the tenacious oxide sidered in the experimental programme and layer must first be removed, this being especially their performance assessed in terms of deposit important if the thickness of the platinum deposit appearance and adhesion, performance under is to be greater than 2 to 3 micrometres, as is conditions and the initial substrate generally required for industrial use. weight loss. Adherent platinum In a recent article M. Pushpavanam and S. R. up to 8 micrometres thick, with good corrosion Natarajan of the Central Electrochemical resistance, were produced by direct deposition Research Institute, Karaikudi, India, describe after the titanium substrate had been treated in experiments carried out to identify a titanium a solution of sodium fluoride, hydrochloric acid pretreatment procedure that would facilitate the and acetic acid; the optimised conditions being direct electrodeposition of platinum ffom a dini- identified in the article. P.E.S.

Platinum Rev., 1994, 38, (4) 165