Chikahide Kanadani

Ionic Liquids of Cationic Sandwich Complexes

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C(5)H(4)R(1))(C(5)H(4)R(2))][Tf(2)N] (M=Fe, Co) and arene-ferrocenium ILs [Fe(C(5)H(4)R(1))(C(6)H(5)R(2))][Tf(2)N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. (57)Fe Mössbauer spectroscopy was applied to [Fe(C(5)H(4)nBu)(2)][Tf(2)N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL.

Homochiral 1D helical chain based on an achiral Cu(II) complex.

Self-assembly of an achiral [Cu(L)] complex produced a homochiral helical chain [Cu(L)](3)·2H(2)O (1) (L = 2-dimethylaminoethyl(oxamato)). Interestingly, complex 1 obtained in our laboratory exhibits only a left-handed helical chain without any chiral source. Single-crystal X-ray analysis revealed the absolute structure and homochirality of its helical chain structure in the space group of P3(2). Solid-state circular dichroism (CD) spectra confirmed the high enantio excess of the crystals obtained in different synthesis batches. Magnetic susceptibility measurements reveal a relatively strong intrachain antiferromagnetic interaction between Cu(II) centers via an oxamato bridge (J = -74.4 cm(-1)).

Pressure-induced instability of magnetic order in Kondo-lattice system: Neutron diffraction study of the pseudo-binary alloy system Ce(Ru0.90Rh0.10)2(Si1-yGey)2

Neutron diffraction experiments have been carried out to study the nature of the magnetic order of the pseudo-binary alloy system Ce(Ru 0.90 Rh 0.10 ) 2 (Si 1- y Ge y ) 2 . Response of the ordered atomic magnetic moment, µ, the transition temperature, T N , and the magnitude of the magnetic modulation vector, q , to the chemical pressure and also to the applied hydrostatic pressure, P , were examined at low temperatures. When y changes, all of µ, T N and q show a sudden alteration of the manner of the y -dependence at around y ∼0.08. The P -dependence of q shows quite different features for different y s of 0.0, 0.2 and 0.25. On the basis of these observations the possibility of a pressure-induced alternation of the magnetic regime of the order is discussed.

Interfacial disorder and magnetic frustration in epitaxial Fe/Cr/Fe trilayers studied by thermoremanent magnetization

In order to investigate the relaxation phenomena in Fe/Cr(001) system with various degrees of interfacial magnetic frustration, we have epitaxially grown Fe/Cr/Fe(001) trilayers on MgO(001) substrate under several thermal conditions by using molecular beam epitaxy (MBE) technique, and measured the time dependence of the thermoremanent magnetization (TRM) in the absence of magnetic field after field cooling process from 300 K to a measuring temperature 250 K under a magnetic field of 100 Oe after a waiting time tw = 0 ~ 100 min. The reflection high energy electron diffraction (RHEED) was employed for confirming the epitaxial growth and for evaluating degree of the interfacial flatness in each sample. From the experimental results, we found that 1) all the present epitaxially grown Fe/Cr/Fe(001) trilayers are ferromagnetic at 300 K, 2) the TRM shows the logarithmic time dependence with larger magnetic viscosity coefficient for the samples which have more disordered interface relative to the other samples, and 3) the most disordered sample shows clearly tw dependence as observed in spin glasses. These results indicate that the interfacial magnetic frustration in the epitaxial Fe/Cr(001) system increases with increasing the interfacial disorder.

Magnetization measurements under pressure for the heavy-fermion compounds Ce(Ru0.9Rh0.1)2(Si1−yGey)2

Recently, it was reported that a phase transition from the spin density wave (SDW) phase to the localized f-electron antiferromagnetic (LAF) phase in the heavy fermion compounds Ce(Ru0.9Rh0.1)2(Si1−yGey)2 (CRRSG0.1/y) around y = 0.26. It is induced by reduction of the cf-hybridization due to the volume effect with increasing the Ge-concentration, y. In this work, we performed magnetization measurements for several y of CRRSG0.1/y at ambient pressure and those under pressure (P) for CRRSG0.1/0.3 with use of a clamp-type pressure cell for the MPMS magnetometer. Applying pressure for y = 0.30, the TN decreases discontinuously around P ≊ 0.12 GPa, which suggests a first order phase transition from the LAF phase to the SDW phase.

Phase transition between the itinerant and the localized antiferromagnetic orders in

We have studied on the shift of the itinerant-electron-type magnetic order (SDW) to localized-electron-type antiferromagnetic order (LAF) in the heavy fermion system Ce(Ru0.9Rh0.1)2(Si1-yGey)2Ce(Ru0.9Rh0.1)2(Si1-yGey)2. The strength of the cf-hybridization in Ce(Ru0.9Rh0.1)2Si2Ce(Ru0.9Rh0.1)2Si2 is reduced by substituting Ge for Si. The electrical resistivity of the y=0.3y=0.3 sample shows a sharp downturn anomaly at TNTN indicating that the magnetic order of this compound is of the LAF. On the other hand, in the samples with y⩽0.2y⩽0.2, the resistivity shows an sharp upturn anomaly at TNTN supposedly due to the energy gap at the Fermi surface associating with the onset of the SDW. The most remarkable result is that for y=0.26y=0.26 the resistivity shows both of the downturn and the upturn anomaly in the same sample, which strongly indicates a first-order phase transition between the LAF order and the SDW order.