The magnetic anisotropy of Tb-phthalocyanine films effected by molecular orientation

Polarized infrared microscopy has been used for forensic purposes to differentiate among polymer fibers. Dichroism can be used to compare and discriminate between different polyester fibers, including those composed of polyethylene terephthalate that are frequently encountered during criminal casework. In the fiber manufacturering process, fibers are drawn to develop molecular orientation and crystallinity. Macromolecular chains are oriented with respect to the long axis of the fiber. It is desirable to determine the relationship between the molecular orientation and stretching properties. This is particularly useful on a single fiber basis. Polarized spectroscopic differences observed from a single fiber are proposed to reveal the extent of molecular orientation within that single fiber. In the work presented, we compared the dichroic ratio between unstretched and stretched polyester fibers, and the transition point between the two forms of the same fiber. These techniques were applied to different polyester fibers. A fiber stretching device was fabricated for use on the instrument (IRμs, Spectra-Tech) stage. Tension was applied with a micrometer screw until a “neck” was produced in the stretched fiber. Spectra were obtained from an area of 24×48 μm. A wire-grid polarizer was used between the source and the sample.

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TEM Study of Co/Pd and Co/Au Multilayers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151015 ◽

1993 ◽

Vol 51 ◽

pp. 1036-1037

Author(s):

A.E.M. De Veirman ◽

F.J.G. Hakkens ◽

W.M.J. Coene ◽

F.J.A. den Broeder

Keyword(s):

Magnetic Anisotropy ◽

Ion Beam ◽

Perpendicular Magnetic Anisotropy ◽

Optical Recording ◽

Magnetic Multilayer ◽

Ion Beam Sputtering ◽

Cross Sectional ◽

Transmission Electron ◽

Beam Sputtering ◽

Substrate Temperatures

There is currently great interest in magnetic multilayer (ML) thin films (see e.g.), because they display some interesting magnetic properties. Co/Pd and Co/Au ML systems exhibit perpendicular magnetic anisotropy below certain Co layer thicknesses, which makes them candidates for applications in the field of magneto-optical recording. It has been found that the magnetic anisotropy of a particular system strongly depends on the preparation method (vapour deposition, sputtering, ion beam sputtering) as well as on the substrate, underlayer and deposition temperature. In order to get a better understanding of the correlation between microstructure and properties a thorough cross-sectional transmission electron microscopy (XTEM) study of vapour deposited Co/Pd and Co/Au (111) MLs was undertaken (for more detailed results see ref.).The Co/Pd films (with fixed Pd thickness of 2.2 nm) were deposited on mica substrates at substrate temperatures Ts of 20°C and 200°C, after prior deposition of a 100 nm Pd underlayer at 450°C.

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Observing the relaxation of molecular orientation in sheared liquid crystalline polymer solutions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178598 ◽

1990 ◽

Vol 48 (4) ◽

pp. 1092-1093

Author(s):

Wendy Putnam ◽

Christopher Viney

Keyword(s):

Molecular Orientation ◽

Liquid Crystalline Polymer ◽

Liquid Crystalline ◽

Crystalline Polymer ◽

Polymer Processing ◽

Molecular Alignment ◽

Global Alignment ◽

Shear Direction ◽

Axial Strength ◽

Strength And Stiffness

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.

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