Liquid crystal electropolymerisation under magnetic field and resultant linear polarised electrochromism

The electrochemical preparation of poly(3,4-ethylenedioxythiophene) (PEDOT) is conducted in liquid crystal (LC) electrolyte solution with nematic (N), cholesteric (Ch*), and smectic A (SmA) phases under a magnetic field. The polymer imprints the molecular arrangement of the LC electrolyte during the polymerisation process. The oriented polymers thus obtained displays optical texture characteristics that resemble those of the LC electrolyte solution. Especially, visualization of SmA domain through PEDOTfibrils is achieved. The magnetic alignment produces linear optical polarisation for the polymers. The PEDOTs thus prepared exhibit good reproducible electroactivity. The present electropolymerisation under magnetic field affords polymer films with linear polarised electrochromism

Direct observation of remarkable crystalline-electric-field effect in quasi-two-dimensional antiferromagnet Er5Ir4Si10 single crystal by low-temperature specific heat

金沢大学理工研究域数物科学系We have intensively investigated the antiferromagnetic phase transition in the ternary rare-earth metal silicide Er5Ir4Si10 single crystal by performing the high-resolution measurement of the low-temperature specific heat under zero-magnetic field and the AC magnetization. In the temperature dependence of important physical quantities associated with the antiferromagnetic phase transition, we have observed anomalies with the antiferromagnetic long-range ordering at Neel temperature T N. We have confirmed that T N is 3.5 K. In addition, we have first observed two surprising results. Firstly, a shoulder was observed in the vicinity of 2 K in addition to the sharp peak at T N corresponding to the antiferromagnetic phase transition in the high-resolution measurement of the low-temperature specific heat. Secondly, the anomaly of the AC magnetization at T N depends to the magnetic field direction. We have clearly observed the anomaly of the AC magnetization at T N when the AC magnetic field orientation is parallel to the c-axis, whereas we have observed no anomaly of the AC magnetization at T N when the AC magnetic field orientation is perpendicular to the c-axis. These results clarify that our Er5Ir4Si10 single crystal is a quasi-two-dimensional antiferromagnet and has no three-dimensional magnetic structure of the Er3+ local moments. However, we have observed a peak of the AC magnetization around 2 K when the AC magnetic field orientation is perpendicular to the c-axis. This temperature corresponds to that at which a shoulder is observed in the measurement of the low-temperature specific heat. Furthermore, we have observed no frequency dependence of the AC magnetization which is ordinarily observed in the spin glass state. This result means that there is no disorder in our Er5Ir4Si10 single crystal because the crystal structure of Er5Ir4Si10 has the tetragonal crystal structure in which the octagons of Er3+ ions are stacked. In addition, both tetragons and octagons of Er3+ local moments have no magnetic frustration. At last we can conclude that both the shoulder of the low-temperature specific heat in the vicinity of 2 K and the peak of the AC magnetization around 2 K, which is only observed when the AC magnetic field orientation is perpendicular to the c-axis, correspond to the crystalline-electric-effect in the plane which is perpendicular to the c-axis of the tetragonal crystal structure. © 2008 Elsevier B.V. All rights reserved

Measurement of de Haas-van Alphen Effect with Hybrid Magnet(Transport and Fermiology)

An apparatus to measure the de Haas-van Alphen effect in steady high magnetic field has been constructed by using hybrid magnets at Tohoku University. Fermi surfaces were investigated on cuprate high-temperature superconductor and rare earth antimonide. The spectral analyses were performed by using the maximum entropy method as well as the Fourier transformation. In magnetically oriented YBa_2Cu_3O_ and Tl_2Ba_2CuO_ powder , the spectral density shows a peak at 456 T and 400 T, respectively. A slight change of extremal cross-section was found in PrSb above 15 T

Antiferromagnetic transition in ternary rare-earth metal silicide Er5Ir4Si10 single crystal

金沢大学理工研究域数物科学系We have precisely investigated the antiferromagnetic phase transition in the ternary rare-earth metal silicide Er5Ir4Si10 single crystal by performing the high-resolution measurement of the low-temperature specific heat under zero-magnetic field and the AC magnetization. In the temperature dependence of important physical quantities associated with the antiferromagnetic phase transition, we have observed anomalies associated with the antiferromagnetic long-range ordering at Neel temperature TN. We have confirmed that TN is 3.5 K. In addition, we have first observed two surprising results. Firstly, a shoulder was observed in the vicinity of 2 K in addition to the sharp peak at TN corresponding to the antiferromagnetic long-range ordering in the high-resolution measurement of the low-temperature specific heat. Secondly, the anomaly of the AC magnetization at TN depends on the magnetic field direction. Though we have clearly observed the anomaly of the AC magnetization associated with the antiferromagnetic phase transition at TN when the AC magnetic field direction is parallel to the c-axis, we have observed no anomaly of the AC magnetization at TN when the AC magnetic field orientation is perpendicular to the c-axis. These results clarify that our Er5Ir4Si10 single crystal is a quasi-two-dimensional antiferromagnet and then has no magnetic structure of the Er3+ local moments. However, we have observed a peak of the AC magnetization at around 2 K when the AC magnetic field is perpendicular to the c-axis. This temperature corresponds to that at which a shoulder is observed in the high-resolution measurement of the low-temperature specific heat. Furthermore, we have observed no frequency dependence of the AC magnetization which is ordinarily observed in the spin glass state. This result means that there is no disorder in our Er5Ir4Si10 single crystal because the crystal structure of Er5Ir4Si10 has the tetragonal crystal structure in which the octagons of Er3+ ions are stacked. In addition, both the tetragons and the octagons of Er3+ local moments have no magnetic frustration. At last, we can conclude that both the shoulder of the low-temperature specific heat in the vicinity of 2 K and the peak of the AC magnetization at around 2 K, which is only observed when the AC magnetic field direction is perpendicular to the c-axis, correspond to the crystalline electric field effect in the plane which is perpendicular to the c-axis of the tetragonal crystal structure. © 2008 Elsevier B.V. All rights reserved

Effect of pressure on the magnetic, transport, and thermal-transport properties of the electron-doped manganite CaMn1−x_{1-x}Sbx_{x}O3_{3}

We have demonstrated the effect of hydrostatic pressure on magnetic and transport properties, and thermal transport properties in electron-doped manganites CaMn$_{1-x}$Sb$_{x}$O$_{3}$. The substitution of Sb$^{5+}$ ion for Mn $^{4+}$site of the parent matrix causes one-electron doping with the chemical formula CaMn$^{4+}_{1-2x}$Mn$^{3+}_{x}$Sb$^{5+}_{x}$O$_{3}$ accompanied by a monotonous increase in unit cell volume as a function of $x$. Upon increasing the doping level of Sb, the magnitudes of both electrical resistivity and negative Seebeck coefficient are suppressed at high temperatures, indicating the electron doping. Anomalous diamagnetic behaviors at $x=0.05$ and 0.08 are clearly observed in field cooled dc magnetization. The effect of hydrostatic pressure on dc magnetization is in contrast to the chemical pressure effect due to Sb doping. The dynamical effect of ac magnetic susceptibility measurement points to the formation of the magnetically frustrated clusters such as FM clusters embedded in canted AFM matrix.Comment: 12 pages,11 figures, 3 table

Effect of pressure on the magnetic, transport, and thermal-transport properties of the electron-doped manganite CaMn1−x_{1-x}Sbx_{x}O3_{3}

We have demonstrated the effect of hydrostatic pressure on magnetic and transport properties, and thermal transport properties in electron-doped manganites CaMn$_{1-x}$Sb$_{x}$O$_{3}$. The substitution of Sb$^{5+}$ ion for Mn $^{4+}$site of the parent matrix causes one-electron doping with the chemical formula CaMn$^{4+}_{1-2x}$Mn$^{3+}_{x}$Sb$^{5+}_{x}$O$_{3}$ accompanied by a monotonous increase in unit cell volume as a function of $x$. Upon increasing the doping level of Sb, the magnitudes of both electrical resistivity and negative Seebeck coefficient are suppressed at high temperatures, indicating the electron doping. Anomalous diamagnetic behaviors at $x=0.05$ and 0.08 are clearly observed in field cooled dc magnetization. The effect of hydrostatic pressure on dc magnetization is in contrast to the chemical pressure effect due to Sb doping. The dynamical effect of ac magnetic susceptibility measurement points to the formation of the magnetically frustrated clusters such as FM clusters embedded in canted AFM matrix.Comment: 12 pages,11 figures, 3 table