Upon substitution of Sn for Zn,the Curie temperature of Mn 3 ZnC is lowered from 380 to 375 K for Mn 3 Zn 0.95 Sn 0.05 C and to 305 K for Mn 3 Zn 0.75 Sn 0.25 C.In accordance with the second-order ferromagneticparamagnetic transition,a room-temperature magnetocaloric effect without thermal and magnetic hysteresis is observed over a wide temperature range.The maximum value of the magnetic-entropy change S M for a magnetic-field change from 0 to 5 T is 2.42 J.kg 1.K 1 at 386 K for Mn 3 Zn 0.95 Sn 0.05 C and 1.70 J.kg 1.K 1 at 308 K for Mn 3 Zn 0.75 Sn 0.25 C.Meanwhile,substitution of Cr for Mn lowers the temperature of ferromagneticferrimagnetic transition from 233 K for Mn 3 ZnC to 230 K for Mn 2.9 Cr 0.1 ZnC and to 175 K for Mn 2.1 Cr 0.9 ZnC.An inverse magnetocaloric effect with S M equal to 0.28 J.kg 1.K 1 at 223 K for a field change from 0 to 1.47 T is observed for Mn 2.9 Cr 0.1 ZnC.
Metallosupramolecular coordination polyelectrolyte, Fe(II)-metalloviologen(FEN), was prepared by the reaction of Fe(II) with a novel bisterpyridine ligand. As active components, FENs could be assembled into electrochromic multilayer films with negative charged polystyrene sulfate(PSS) by the sequential deposition layer-by-layer technique. Numerous analytical instruments, such as UV-Vis spectroscopy, atomic force microscopy(AFM), tunneling electron microscopy(TEM), zeta-potential measurement and electrochemical measurement have been utilized to characterize their morphology, optical and electrochromic properties. It has been observed that as-prepared films exhibited multi-colour changes by triggering with different potentials. However, the low optical contrast of multilayer films would limit their further applications. In order to overcome this problem, semiconductor TiO2 nanoparticles(TiO2) were incorporated into FEN multilayers by layer-by-layer approach. By carefully optimizing the film structure, as-resulted hybrid films containing FEN, TiO2 and PSS exhibited high optical contrast, suitable response time and long-term stability. Such hybrid films should be promising candidates to meet the requirements for developing flexible displays and electrochromic devices.
WANG RuiLIU Dong-xuYANG YangYU Da-huiYAO Wei-guoDENG Chang-chunDONG Wen-fei
The epitaxial Mn_(0.98)Cr_(0.02)Te films on single crystal Al_2O_3(0001) substrates were prepared by pulsed laser deposition.The X-ray diffraction and scanning electron microscopy results showed that the good continuous epitaxial film was obtained with substrate temperature of 500 ℃.When the substrate temperature reached700 ℃,the film was island growth and the manganese oxides phase appeared.The temperature dependence of both the magnetization and electrical resistance showed a sharp rise at around 60 K due to the magnetoelastic coupling.The temperature dependence of the electrical resistance of Mn_(0.98)Cr_(0.02)Te provided evidence for a transition from the metallic to semiconducting state at 305 K due to the spin disorder scattering with a large contribution from the influence of magnon drag.
