Behaviour of ferrocholesterics under external magnetic fields |
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Institution: | 1. Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh;2. Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia |
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Abstract: | The influence of an external magnetic field on the orientational behaviour of a ferrocholesteric with a positive magnetic anisotropy is investigated. Both the phenomena arising when the field was switched on or switched off are considered. It is found that the field needed for a ferrocholesteric–ferronematic transition BFC↑ is higher when compared to that obtained for the pure cholesteric (BC↑). A similar result was obtained when estimating the critical field for the homeotropic ferronematic–ferrocholesteric (focal conic) transition, occurring when the magnetic field was decreased or switched off. We found that BFC↓>BC↓. These results are explained when considering that the magnetic moments of the magnetic powder are not oriented parallel to the liquid crystal molecular directors, therefore hindering their orientation under a magnetic field. |
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