Abstract
Liquid crystalline (LC) organic radicals were expected to show a novel non-linear magnetic response to external magnetic and electric fields due to their coherent collective molecular motion. We have found that a series of chiral and achiral all-organic LC radicals having one or two five-membered cyclic nitroxide radical (PROXYL) units in the core position and, thereby, with a negative dielectric anisotropy exhibit spin glass (SG)-like superparamagnetic features, such as a magnetic hysteresis (referred to as ‘positive magneto-LC effect’), and thermal and impurity effects during a heating and cooling cycle in weak magnetic fields. Furthermore, for the first time, a nonlinear magneto-electric (ME) effect has been detected with respect to one of the LC radicals showing a ferroelectric (chiral Smectic C) phase. The mechanism of the positive magneto-LC effect is proposed and discussed by comparison of our experimental results with the well-known magnetic properties of SG materials and on the basis of the experimental results of a nonlinear ME effect. A recent theoretical study by means of molecular dynamic simulation and density functional theory calculations suggesting the high possibility of conservation of the memory of spin-spin interactions between magnetic moments owing to the ceaseless molecular contacts in the LC and isotropic states is briefly mentioned as well.
Highlights
Following the birth and establishment of ‘Einsteinian general theory of relativity’ and ‘quantum theory and mechanics’ at the beginning of the 20th century [1], the ‘complexity theory’ developed rapidly since the 1970s is recognized as one of the paradigm shifts or innovations in science in the same century [2,3,4]
The result that the super-para-magnetic domains augmented with the increasing ee value of the liquid crystalline (LC) compounds (See Section 4.1.1) is likely to demonstrate the with the increasing ee value of the LC compounds (See Section 4.1.1) is likely to demonstrate the correlation of the positive magneto-LC effect and the breaking of space inversion symmetry
Uncover the mechanism for the birth and grow of super-para-magnetic domains, which will lead to the elucidation of the microscopic mechanism of positive magneto-LC effect that LC nitroxide uncover the mechanism for the birth and grow of super-para-magnetic domains, which will lead to the elucidation of the microscopic mechanism of positive magneto-LC effect that LC nitroxide radicals exhibited
Summary
Following the birth and establishment of ‘Einsteinian general theory of relativity’ and ‘quantum theory and mechanics’ at the beginning of the 20th century [1], the ‘complexity theory’ developed rapidly since the 1970s is recognized as one of the paradigm shifts or innovations in science in the same century [2,3,4]. Phases are considered to be a sort of complexity system consisting of nonequilibrium dynamic states They are so sensitive to external stimuli, such as electric or magnetic field, heat, light, due to the molecular motion and the coherent collective properties of molecules in the LC state [8]. LC compounds had attracted greatproperties interest as soft materials to enhance were anticipated to exhibit unique magnetic interactions and, thereby, unconventional magnetothe effect of magnetic fields on the electric and optical properties of liquid crystals. They were anticipated electric [17,18,19,20].
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