We combine old, unpublished data on ionic liquids containing quaternary ammonium cations with new data on salts of aromatic cations containing a variety of anions, to demonstrate the existence for ionic liquids of an unexpectedly wide range of liquid fragilities. The pattern is one now familiar for other liquids. Here, the pattern is important in determining the relative fluid properties at ambient temperatures. We find that the optimization of ionic liquids for ambient temperature applications requiring low-vapor-pressure fluid phases involves the proper interplay of both cohesive energy and fragility factors. The cohesive energy is discussed in terms of the coulomb and van der Waals contributions to the attractive part of the pair potential. On the basis of the relation between the glass-transition temperature and the molar volume for salts with less-polarizable anions, we find evidence for a broad minimum in the ionic liquid cohesive energy at an internuclear separation of ca. 0.6 nm. This minimum lies between those of the BF 4 and TFSIanions for the small quaternary ammonium cations of this study. The minimum is expected to be narrower and less well-defined for salts with polarizable anions. The relation of fluidity to conductance is considered in terms of a Walden plot that is shown to provide a useful basis for organizing the observations on ionic liquids and solutions. Low vapor pressure and ideal Walden products are intimately related.

Superconducting thin films of Y-Ba-Cu oxide have been prepared on yttria-stabilized zirconia substrates using metal trifluoroacetate spin-on precursors. The films exhibit an extremely sharp resistive transition with zero resistance at temperatures as high as 94 K. The superconducting phase is formed by a three-step process: (a) decomposition of the spun-on trifluoroacetate film to the fluorides, (b) conversion of the fluorides to oxides by reacting with water vapor, and (c) annealing followed by slow cooling in oxygen. The properties of the films depend on the amount of conversion of the fluorides by reaction with water. Films which show the presence of some unreacted barium fluoride have strong c-axis normal preferred orientation, with a sharp resistive transition. When all the barium fluoride is converted, the film is more randomly oriented and exhibits a broader transition to zero resistance.

The continuous and rapid increase of areal density in magnetic data storage systems required a continuous increase of the coercivity of the storage media. In order to be able to record on these everhigher-coercivity media, new soft magnetic materials for pole tips with increased magnetic moment had to be developed. Significant progress has been made during the last few years in electroplating alloys with high saturation magnetic flux density for use in writing heads. We review recent progress made in this area, with particular emphasis on the work done at IBM since the review paper on the subject was published in this journal in 1998 by Andricacos and Robertson. Reviewed here are the high-moment alloys of NiFe, particularly in the very high iron range [an extension of permalloy (Ni 80 Fe 20) and Ni 45 Fe 55 ]; very-high-cobalt CoFeCu alloys; ternary CoNiFe; and binary iron-rich CoFe alloys. With the latter binary alloy films, we have demonstrated that it is possible to reach by electroplating the saturation flux density limit of 2.4-2.5 T reported for cast alloys. Since the electroplating of good-magneticquality iron-rich CoFe alloys posed a considerable challenge, the behavior of the CoFe plating system was studied in detail, using in situ surface pH measurements and a rotating-cylinder Hull cell.

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