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We succeeded in growing single crystals of SrAl 4 and related compounds with the BaAl 4 -type tetragonal structure by the self-flux method, and measured the electrical resistivity, magnetic susceptibility, Hall coefficient, thermoelectric power, and de Haas–van Alphen (dHvA) effect. A plausible characteristic feature of the charge density wave (CDW) was observed below T CDW = 243 K in SrAl 4 . We also studied an effect of pressure on the electronic state in SrAl 4 by measuring the electrical resistivity and thermoelectric power. T CDW is found to decrease with increasing pressure, with a rate of dT CDW / dP = −12.5 K/GPa. To clarify the Fermi surface nesting, we studied the Fermi surface in SrAl 4 , which is found to be different from the Fermi surfaces of the similar compounds SrGa 4 , BaGa 4 , and BaAl 4 without CDW. The Fermi surfaces in these compounds were determined from the dHvA experiments, together with the energy band calculations.

Thin films of mesoporous lamellar nickel oxides and nanotube manganese oxides were electrochemically fabricated on indium tin oxide (ITO) glass using sodium n-dodecyl sulfate (SDS) as a template agent under different controlled potentials in 10 mM Ni(NO 3 ) 2 and 100 mM MnSO 4 solutions. Electrochromic characterization together with the morphological observation by transmission electron microscopy (TEM), structure analysis by X-ray diffraction (XRD) and electron diffraction (ED) was made. Nickel and manganese oxide films of nanostructures, compared with conventional structure ones, showed marked changes in optical transmittance and electric charge with regard to the electrochromic reactions in aqueous solution of 100 mM LiOH. However, in a non-aqueous γ-butyrolactone (GBL) solution of 100 mM Bis(trifluoromethane)sulfonimide lithium, the nickel oxide films did not show any notable electrochromic reactions, while the manganese oxide films of both nanostructure and conventional structure are electrochromically active and the effect of nanostructure on the electrochromic properties was remarkable.

We studied the change of the Fermi surface properties in antiferromagnets CeIn 3 and CeRhIn 5 via the dHvA experiments under pressure. We found the abrupt change of the Fermi surface at the critical pressure P c , where the magnetic ordering state changes to the paramagnetic one. The change of the Fermi surface indicates that the 4f-electron character is changed from localized to itinerant in CeIn 3 and CeRhIn 5 at P c . Namely, the 4f-electron contributes to the volume of the Fermi surface above P c . Interestingly, the pressure-induced heavy fermion state with large effective mass was observed around P c , where the pressure-induced superconductivity appears. We also discuss the Fermi surface properties in the system without inversion symmetry in the crystal structure as in CePt 3 Si and CeTX 3 (T:Co, Ir, Rh, X:Si, Ge). The spin–orbit interaction due to the lack of inversion symmetry brings about a splitting of the Fermi surface, which is important for considering the formation of Cooper pair.

When pressure is applied to cerium and uranium compounds, the magnetic ordering temperature is suppressed and becomes zero at a critical pressure P c . Around P c , non-Fermi liquid and/or superconductivity are observed. We clarified a change of the electronic state via a de Haas–van Alphen (dHvA) experiment when pressure crosses P c . The dHvA experiment under pressure was done for the antiferromagnets CeRh 2 Si 2 and CeRhIn 5 , and for a ferromagnet UGe 2 . We found an abrupt change of the Fermi surface for CeRh 2 Si 2 and UGe2 when crossing P c , indicating a first-order like phase transition. For CeRhIn 5 , the topology of the Fermi surface was unchanged, but the cyclotron mass increased steeply above 1.6 Gpa, where superconductivity sets in.

We carried out the de Haas–van Alphen (dHvA) experiment under pressure to clarify the nature of f-electron compounds of CeRh2Si2, UGe2 and CeCoIn5. With increasing pressure, the Neel temperature T N =36 K in CeRh2Si2 and the Curie temperature T C =52 K in UGe2 decrease, and a quantum critical point corresponding to the extrapolation TN or TC→0 is reached at the critical pressure pc≃1.06 and 1.52 GPa, respectively. Experimental results indicate a discontinuous change of the Fermi surface in CeRh2Si2 and UGe2 when the pressure crosses pc. A heavy fermion superconductor CeCoIn5 with a quasi-two dimensional Fermi surface was found to be located in the vicinity of the quantum critical point.

Potassium clusters arrayed in zeolite A are known to show ferromagnetic properties at low temperature. The origin of the spontaneous magnetization has been explained by a model of spin-canting in an antiferromagnetically ordered state. The direct information for the magnetic structure, however, has not been obtained so far. In the present work, we measure the neutron powder diffraction by using pulsed neutron source at KEK-KENS below and above the Curie temperature. No significant temperature-dependence was, however, obtained within the statistical errors, namely, magnetic scattering could not be detected separately. We also estimate the intensity of magnetic scattering by assuming some possible magnetic structures with considering the magnetic form factor of the cluster wave function. The intensity of magnetic scattering is estimated to be extremely weak and higher S/N of ∼104 or more is required to detect the magnetic scattering of this material.

We studied systematically a series of the ternary compounds RRhIn 5 (R: rare earth) which were grown in the single crystalline form by means of the flux method. Most of these compounds order antiferromagnetically at low temperatures, except for R = Y, La, Pr and Yb. The observed temperature dependence of the specific heat and the anisotropic features in the magnetic susceptibility and magnetization have been analyzed on the basis of the crystalline electric field (CEF) model, and an interesting relationship between the anisotropic exchange interaction and the CEF effect is obtained for RRhIn 5 compounds.

The pressure-doping technique was developed for further loading of guest potassium metal into porous crystals of zeolite beyond the upper limit at ambient pressure. A doping pressure dependence of the magnetic property of potassium clusters in cages of zeolite A is measured up to 320 MPa. The Curie constant monotonically decreases with increase in the doping pressure and shows very small values above 250 MPa. The magnetic susceptibility at 2 K, however, gradually increases and has a peak at 200 MPa. Observed decrease in the Curie constant is explained by the increase in the loading density of potassium. Simultaneously, the increase in the magnetic susceptibility at 2 K is explained by the superparamagnetism of ferromagnetic domains. A possible mechanism of change in the magnetic properties is discussed.

We report the novel phase diagram of superconductivity (SC) and antiferromagnetism (AFM) in heavy-fermion (HF) pressure( P )-induced superconductors CeRhIn 5 and CeIn 5 through nuclear-quadrupole-resonance (NQR) measurements under P . The P -induced superconductivity in CeRhIn 5 coexists with AFM on a microscopic level in P =1.5–1.9 GPa. By contrast, in CeIn 3 , the P -induced phase separation of AFM and paramagnetism (PM) takes place without any trace of a quantum phase transition. The outstanding finding is that SC sets in at both the phases magnetically separated into AFM and PM in P =2.28–2.5 GPa.

We have studied the metamagnetism in PrCu2 via the magnetostriction. The metamagnetic transition accompanies a conversion between an easy and a hard axes in magnetization and also a huge magnetostriction. It is due to the magnetoelastic effect arising from the quadrupolar interaction, bringing about the rotation of the quadrupole moment.

We report the discovery of novel phases in CeIn3 on the verge of antiferromagnetism (AFM) through the In-nuclear quadrupole resonance (NQR) measurements. We have found that even though a pressure (P)-induced phase separation into AFM and paramagnetism (PM) takes place, a novel superconductivity (SC), which is induced without strong spin fluctuations, has been found to coexist with AFM on a microscopic level. We propose that the magnetic excitations such as spin-density fluctuations induced by the first-order magnetic phase transition might mediate attractive interaction to form Cooper pairs.

We measured the specific heat, thermal expansion coefficient, magnetization, electrical resistivity, magnetoresistance and de Haas–van Alphen (dHvA) effect in PrSn 3 . The dense Kondo effect was confirmed from a negative magnetoresistance and the presence of heavy electrons with the cyclotron effective mass of 8–9 m 0 for the main Fermi surface. A magnetic anisotropy was found below T N , having an easy axis of 〈1 1 0〉.

We succeeded in growing a high-quality single crystal of CeRh2Si2 with a residual resistivity ratio of 110. Under a pressure of 1.1 GPa, superconductivity is found below Tc=0.38 K, where a Neel temperature of TN=36 K is suppressed down to almost zero.

We found the field-induced antiferro-quadrupole (AFQ) ordering in the Pr-based heavy fermion superconductor PrOs4Sb12 by means of neutron scattering. The field-induced staggered moment and the field dependence of the crystal field excitation spectra can be well understood in terms of the mean field Hamiltonian based on the singlet Γ1 with triplet Γ4 first excited state, where the quadrupolar interaction plays essential role for the AFQ ordering.

Neutron scattering experiments have been performed to reveal the magnetic excitation in ferromagnet CeAgSb2. Crystalline electric field excitations were observed at 5.2 and 12.5 meV in the paramagnetic state. Our analysis concluded that | ± 1 2 〉 is the ground state. The observed ferromagnetic moment is in good agreement with the ground-state saturation moment, g J μ B J z ∼0.43 μ B . The spontaneous moment along the c-axis decreases with increasing the field perpendicular to the c-axis, and disappear at the critical field Hc, where the magnetization curve shows the kink behavior.

We have studied the de Haas–van Alphen (dHvA) effect under pressure for an antiferromagnet CeRhIn5, where the antiferromagnetic state is changed into the superconducting state at higher pressures than 1.6 GPa . It is clarified from the present dHvA experiment that the topology of the Fermi surface is unchanged up to 2.1 GPa but the cyclotron mass increases strongly above 1.6 GPa . Superconductivity is found to be realized in this heavy fermion state.

We report evidences for bulk nature and unconventional superconductivity in CeIn 3 at P =2.65 GPa revealed by the measurements of nuclear-spin–lattice-relaxation time ( T 1 ) and ac-susceptibility (ac- χ ). Both the measurements of ac- χ and T 1 have pointed to a superconducting transition at T =95 mK, which is very much lower than an onset temperature T onset =0.15 K at zero resistance. The temperature dependence of 1/ T 1 shows no coherence peak just below T c , indicative of an unconventional nature for the superconductivity.

We observed de Haas-van Alphen (dHvA) oscillations in CeRh2Si2 at 1.3 GPa , higher than the quantum critical pressure p c ≃1.0 GPa . Three observed dHvA branches correspond to the result of the 4f-itinerant model. Their cyclotron masses are large, being 24m0, 29m0 and 31m0, about 4 times larger than the corresponding band masses.

We have measured the AC magnetic susceptibility of single crystals of the heavy fermion compounds CeCu6 and CeNi at temperatures down to 250 μK . The susceptibility of CeCu6 shows a peak at about 2 mK in a zero magnetic field. The peak height along a-axis is about 10 times as large as along b- and c-axis, and decreases to zero in increasing field up to 11 mT. It is likely that the susceptibility of CeNi along c-axis has three peaks: below 350 μK , at 47 mK and at 0.3 K, respectively. The two peaks at lower temperatures are suppressed by a magnetic field. The newly observed peaks in the susceptibilities for CeCu6 and CeNi suggest effects of magnetic impurities rather than of magnetic ordering.

In order to investigate the 5f electronic properties in a ferromagnet UGa2 with the hexagonal structure, we have performed the magnetic, elastic, transport and de Haas–van Alphen experiments. From these properties, the crystal distortion is found to occur below 100 K in the basal plane, which is most likely driven by the development of a ferromagnetic moment oriented along the [1 1 2 0] direction.

We measured the electrical resistivity, magnetoresistance and de Haas–van Alphen effect in PrSn3. The Kondo effect was confirmed from a negative magnetoresistance and the presence of heavy electrons with the cyclotron effective mass m ∗ C =7.43–9.3 m 0 .

A self-consistent band calculation including an orbital polarization is performed for ferromagnetic UGa2 on the basis of an all-electron fully-relativistic spin-polarized LAPW (RSPLAPW) method with exchange-correlation potentials in a local density approximation (LDA). The obtained magnetic moment is composed of the spin of about −2.0 μB and the orbital moment of about 4.9 μB. Accordingly, it can be interpreted as if the configuration were a localized 5f2, though the f character contains about 2.5 as valence electrons. From the band structure, the Fermi surface is constructed in order to analyze frequencies observed by the de Haas–van Alphen (dHvA) effect.

High-field magnetization measurements in a heavy fermion antiferromagnet CeRh2Si2 were performed under high pressures at various temperatures to study the nature of the metamagnetism. Metamagnetic transitions were observed not only in the antiferromagnetic state but also in the paramagnetic state at various pressures. The metamagnetism in CeRh2Si2 does not originate from the rearrangement of antiferromagnetic moments but from the recovery of the local moment from the Kondo singlet state by applying high magnetic fields.

An intermediate valence compound CeNi exhibits a phase transition under pressure, which is associated with the γ–α transition in Ce. To clarify a change of the electronic state under pressure, we measured the de Haas–van Alphen (dHvA) effect under pressure up to 6 kbar using a Cu–Be pressure cell. The dHvA branches are still observed after the phase transition. The topology of the Fermi surface is therefore unchanged. The cyclotron effective mass is, however, reduced from 11 to 3.2m0 for branch e and from 5.4 to 1.2m0 for branch σ when the pressure is changed from 1 bar to 3.7 kbar.

Electrical resistance has been investigated in a high-quality polycrystal of CeRh 2 Si 2 under high pressures of up to 5.4 GPa. We found a resistance drop corresponding to superconductivity in the pressure range from 0.7 to 2.9 GPa. The relative decrease of the resistance shows a maximum in the vicinity of a critical pressure P C . An onset temperature of superconductivity is about 0.6 K.

Angular dependence of the transverse magnetoresistance of a heavy-fermion superconductor UBe13 (Tc=0.9 K) was measured on a single crystal grown by the Al-flux method. The resistivity decreases with increasing the magnetic field at low temperatures, indicating that a magnetic scattering is suppressed by the magnetic field. We observed a remarkable angular dependence in magnetoresistance at 0.45 K under a constant field of 13 T, showing a minimum at the [1 1 0] direction. This anisotropy of magnetoresistance is observed below 4 K. Since the large resistivity (200 μΩ cm) of this compound at low temperatures is attributed to the magnetic scattering by uranium ions, the present anisotropy in the magnetic scattering at low temperatures would give important information about the ground state of 5f electrons.

Magnetic and transport properties have been investigated in the single crystal of CeRh2Si2 under high pressures. We found that the magnetic susceptibility under high pressure shows a broad maximum like CeRu2Si2. In the present pressure range up to 13 kbar where the ordered state is suppressed, no obvious evidence of the superconducting transition is observed down to 50 mK.

We have studied the origin of the cooperative Jahn-Teller effect in PrCu 2 . We have determined the anisotropic phase diagram by measuring the thermal expansion and the magnetostriction in magnetic fields up to 15 T. The Jahn-Teller transition temperature is almost constant for the field along the a- and c -axis, while it decreases with increasing the field along the b -axis. The phase diagram can be explained qualitatively by including the quadrupolar interaction for 〈O xy 〉 in the crystalline electric field Hamiltonian.

A series of carbamato-silver(I) complexes having the formula of MePh2PAg(YZCNR2) (1), (Ph3P)2Ag(YZCNR2) (2), (MePh2P)2Ag(YC(O)NR2) (3), Ph3PAg(YC(O)NR2) (4) (YZ = SS, SSe, SeSe; Y = S, Se; R = Me, Et) and (Ph3P)3Ag2(SC(O)NEt2)2 (5) were prepared. Molecular-weight determinations, conductivity measurements, 1H and 31P NMR spectra indicate that 1 exists as a planar three-coordinate complex involving a bidentate carbamato ligand in solution. The complexes 2 and 3 dissociate into the phosphorus ligand and Ph3PAg(YZCNR2) or MePh2PAg(YC(O)NR2) to considerable extents in solution. On the other hand, 4 exists as an equilibrium mixture of monomeric and oligomeric species in solution. The addition of extra Ph3P to a solution of 4, causes the formation of the bis-phosphine complex, (Ph3P)2Ag(YC(O)NR2), which is a predominant species in solution containing three equivalent amounts of Ph3P at low temperature. It is also concluded that 3, 4 and 5 have less tendencies to exist as disilver(I) species in solution than the copper(I) analogs.

A series of the compounds of formula [M(PR3)2 (XYCNMe2)][Me2SnCl3] (M = Pd(II) and Pt(II); PR3 = PPh3 and PMePh2; X, Y = Se) has been prepared. Conductivity measurements, i.r. and PMR spectra indicate that the complexes are 1:1 electrolytes in solution and the cationic part takes a square planar configuration. The 1H and 31P NMR spectra reveal that abilities of the sulfur and selenium to coordinate with the metal(II) resemble each other closely. The bonding nature of the PR3 Pd(II) and -Pt(II) bonds is also described on the basis of the 31P N MR spectra.