video recorders. This patent shows a scheme for vertical recording using magnetic stylii 15, 30 that sweep in arc-shaped paths across tape 22 while it is supported at 25 by a blunt polepiece 23 energized by coil 18.--MC

4,636,898

43.88.Qg MULTICHANNEL MAGNETIC HEAD

Masaki Suzuki, deceased, and Goro Akashi, assignors to Fuji Photo Film Company

13 January 1987 (Class 360/122); filed 19 July 1985

The narrow tracks on compact cassette tapes may give a fluctuation in output due to tape "waving" from side to side. Such waving is reduced greatly by a head that has a number of grooves milled in its face over which the tape runs, the grooves being at an angle (6 ø optimum) to the running direction of the tape. The angled grooves bias the tape against an edge guide, and also clean dust particles from the tape.--MC

4,636,901

43.88.Qg THIN FILM MAGNETIC HEAD HAVING MAGNETIC LAYERS OF DIFFERENT THICKNESS

AND MANUFACTURING METHOD THEREFOR

Masaki Ohura and Makoto Saito, assignors to Hitachi, Ltd. 13 January 1987 (Class 360/126); filed in Japan 5 February 1982

A head for magnetic recording and playback is made by depositing the cores and coils as thin films. Improved results are obtained when one of the magnetic polepieces is deposited as a thicker layer than the other in a ratio of 1.2 to 1.4 times as thick.--MC

4,657,814

43.88.Qg MAGNETIC RECORDING MEDIUM

Takamitsu Asai and Masaaki Fujiyuma, assignors to Fuji Photo Film Company

14 April 1987 (Class 428/329); filed in Japan 22 November 1982

A high-performance magnetic tape consists of a polyester base with a sublayer of nonmagnetic metal such as A1, Cu, Zn, Sn, Ti, or alloys, sur- mounted by a coating of plate-shaped crystals of barium ferrite in an organic binder.--MC

4,657,824

43.88.Qg VERTICAL MAGNETIC RECORDING MEDIUM WITH AN INTERMETALLIC COMPOUND NUCLEATING LAYER

James K. Howard, assignor to International Business Machines Corporation

14 April 1987 (Class 428/611); filed 28 October 1985

A vertically oriented medium for high-density magnetic recording has an underlayer of intermetallic compound between the substrate and the recording layer. For example, the underlayer is (Co8oCr2o)3W of 5000-,• thickness, resulting in a perpendicular coercivity of 1000 Oe compared to a longitudinal coercivity of 75 Oe.--MC

ß 4,657,816

43.88.Qg FERRoMAGNETIC RECORDING MATERIALS

Mohammed Siddiq, assignor to Memorex Corporation 14 April 1987 {Class 428/403}; filed 19 April 1982

The ferric oxide particles used on most tapes can be improved by treat- ing them with an aqueous solution of cobalt salts, followed by heating, which results in an adsorbed layer of cobalt. This treatment increases the

coercivity from about 300 to about 550 Oe. Here, a layer of iron is deposited on the adsorbed cobalt, and a second cobalt layer is deposited on the iron. The process may be repeated to give many layers, for still higher coercivi- ties.--MC

4,657,819

43.88.Qg FLEXIBLE MAGNETIC RECORDING MEDIUM COMPRISING AN UNDERLYING FILM

HAVING REDUCED IN-PLANE MAGNETIC

ANISOTROPY UNDER A SURFACE FILM HAVING PERPENDICULAR MAGNETIC ANISOTROPY

Hidefumi Funaki, assignor to Anelva Corporation 14 April 1987 {Class 428/458}; filed in Japan 13 March 1984

A preferred record medium for perpendicular high-density magnetic recording has a substrate of polyester film, a permalloy intermediate layer, and a top layer of perpendicularly oriented CoCr. The permalloy layer exhibits a strong anisotropy that is undesirable in disc records, for example. Such anisotropy is remedied by diluting the permalloy 12% to 50% with an alloy of molybdenum and copper.--MC

4,655,167

43.88.Qg APPARATUS FOR MANUFACTURING OF ABRASION RESISTANT MAGNETIC RECORDING

PRODUCT

Kyuzo Nakamura and Yoshifumi Ota, assignors to Nikon Shinku Gijutsu Kabushiki Kaisha

7 April 1987 (Class 118/718); filed in Japan 24 December 1981

Some magnetic tapes are produced by evaporating a thin layer of mag- netic material such as Co-Cr, Co-Ni-P, Fe203, or BaO-Fe20 3 onto a poly- ester base. Such layers are very fragile. Their durability is improved by manufacturing in a divided compartment vacuum chamber where first the magnetic layer is deposited, then its surface is oxidized to improve absorp- tion, and finally a protective lubricant is applied, such as a fatty acid like oleic acid.--MC

4,660,113

43.88.Qg MAGNETORESISTIVE THIN FILM HEAD

Noboru Nomura and Yasuharu Shimeki, assignors to Matsushita Electric Industrial Company

21 April 1987 (Class 360/113); filed in Japan 9 December 1981

Magnetoresistive playback heads depend on the change in electrical resistance of a thin film when subjected to the field of a magnetized record. This patent shows a thin film element that is center tapped and connected in a push-pull or differential circuit, thereby alleviating noise and demagnet- ization that occurs with single ended elements.--MC

4,663,685

43.88.Qg MAGNETORESISTIVE READ TRANSDUCER HAVING PATTERNED LONGITUDINAL BIAS

Ching H. Tsang, assignor to International Business Machines 5 May 1987 (Class 360/113); filed 15 August 1985

This patent discloses another of the many possible ways to magnetical- ly bias a magnetoresistive sensor for playback of tape recordings. The ends of a Ni-Fe thin film sensing strip are in contact with an antiferromagnetic layer that biases the strip longitudinally, while a current through the strip itself produces a perpendicular component that is concentrated by an addi- tional film of soft magnetic material adjacent to the sensing strip.--MC

1871 J. Acaust. Sac. Am. 82(5), Nov. 1987; 0001-4966/87/111871-01500.80; © 1987 Acaust. Sac. Am.; Patent Reviews 1871

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