Magnetic ‘bubble’ material

Aral, Shigeru presented at the First International Conference on Magnetic Bubble Materials, Santa Barbara, CA, January, 1980. 

Ca is replaced by a rare-earth element, resulting in a distorted perovskite stmcture, which is essentially orthorhombic. Orthoferrites, studied extensively in the early 1970s as potential data storage materials based on magnetic bubble domains (10), have been largely replaced by the garnet materials (see... 

Important is the use of light rare earth elonents for production of hard magnetic materials. Most prominent are alloys of samarium with cobalt in the atomic ratio 1 5 or 2 17. It may also be assumed that in further development of these materials on a larger scale that praseodymium, neodymium, lanthanum and also individual heavy rare ecu h elements will be used to achieve particular effects. Interesting is the development of magnetic bubble memories based on gadolinium-galliiimrgarnets. 

Some of the problems seen with the commercially available polyimides such as limited shelf life,gelation and high ionic contamination are traceable to the raw materials themselves. A zone refining technique has been perfected for use with organic materials and these precursors have been used to synthesize ultrapure polyamic acids for IC device applications. The key feature of the synthesis is the use of solid ingots of the dianhydrides. Materials prepared by this technique show low metallic impurities and have been shown to be excellent film formers for a variety of applications. In particular a polyimide derived from PMDA-ODA has been used to passivate magnetic bubble devices. IR techniques coupled with electrical measurements have been used to optimize the cure conditions and a simple resist process has been defined to passivate these devices. Device performance compares well with conventional inorganic insulators. 

The manufacture of thin film products does not only apply to the making of integrated circuits but also magnetic bubble memories, thin film recording heads, tapes and disks. The physical and chemical processes carried out involve heat and mass transfer, momentum transfer, surface phenomena, high temperature chemistry, radiation, etc. Although the material discussed in this book focuses on the manufacture and fundamentals of integrated circuits, many of the basics are applicable to the fabrication of other thin film devices. 

A. P. Malozemoff and J. C. Slonczewski, Magnetic Domain Walls in Bubble Materials, Academic, New York (1979). 

The continuous dynode electron multiplier (channeltron) is another device (Adams and Manley (1965)) which takes advantage of unique properties of amorphous semiconductors and considerable appUed research is devoted to the utilization of vitreous materials for optical mass memories (Ovshinsky (1969) Feinleib et al (1971)) high energy particle detectors (Srinivasan et al (1971)) ultrasonic delay lines (Krause et al (1970)) and magnetic bubble domain memories (Chaudhari etal (1973)). 

The reaction between TDI and castor oil is exothermic and bubbles are produced in the reaction mixture (castor oil contains a few tenths of a percent volatile material that will evaporate as the temperature of the reaction mixture goes up. Some of the bubbles produced are trapped in the mixture as the viscosity increases. Stirring with a teflon coated magnetic spin bar also produces some bubbles). In order to produce elastomers that are bubble free, the reaction is carried out in two stages. 

The development of the bubble domain memory has been remarkable in that since the discovery of the growth induced anisotropy in garnets, problems connected with materials have been relatively few and not too difficult to solve. A major reason is that the different sizes and magnetic properties of the rare earths offer a wide range of choices for the materials designer. 

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