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Fe-doped NiZrSn polycrystalline ingots were prepared using arc melting method. Microstructure and electrical properties of the ingots were investigated. According to the EDX results, the solubility of Fe in the C1 b phase of the NiZrSn is about 2% by arc melting method. The electrical resistivity of low Fe-doped NiZrSn shows semiconducting temperature dependence and the transport gap estimated from activation plot is about 80 meV.

The electrical resistivity and magnetoresistance (MR) of single crystalline α -Ce have been measured under high pressure and low temperature. It is found that the temperature dependence of resistivity ρ ( T ) at low temperature is described as ρ ( T ) = ρ 0 + A T 2 below 10 K, where ρ 0 is the residual resistivity and A is the constant. A decreases significantly as pressure increases, which corresponds to the increase of Kondo temperature T K at high pressure. A seems to be divergent from higher pressures toward 0.3 GPa, which suggests the existence of magnetic phase boundary. MR ratio of α -Ce is positive and enhanced by applying pressure. These results are discussed on the basis of theoretical model presented by Kawakami–Okiji.

The magnetic structure of heavy-fermion antiferromagnets Ce(Ni 1- x Pd x ) 2 Ge 2 proximate to the magnetic instability has been studied by elastic neutron scattering using single crystals. For Ce(Ni 0.65 Pd 0.35 ) 2 Ge 2 , antiferromagnetic ordering with an incommensurate propagation vector q =(1/2,1/2,δ); δ∼0.16 is observed below T N =3.4 K. The integrated intensities of magnetic Bragg peaks at 1.8 K are well fitted by assuming a sine-wave-modulated structure with the amplitude 0.55±0.04 µ B and magnetic moments along [110]. For the compound very near the magnetic instability, Ce(Ni 0.90 Pd 0.10 ) 2 Ge 2 , the ordered moment is expected to be reduced to below 0.1 µ B .

We have developed a clamped piston-cylinder high-pressure cell using NiCrAl alloy and have performed de Haas–van Alphen effect measurements on UGe 2 under hydrostatic pressures up to 17.6 kbar, which exceeds the critical pressure P c where the Curie temperature T C vanishes. We have found that a discontinuous change of the Fermi surface occurs across P c . Quasiparticle effective masses are substantially enhanced near 13 kbar, where the T x anomaly, which occurs below T C in the ferromagnetic phase, is suppressed. Heavy masses (∼40 m e ) are observed near P c on both the ferromagnetic and paramagnetic sides.

We have succeeded in growing a high-quality single crystal of PrNi 2 Al 5 , and have measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. Any magnetic phase transition has not been observed. The crystalline-electric-field (CEF) scheme has been estimated by using the reciprocal susceptibility and a magnetic part of the specific heat. The magnetic anisotropy has been well explained by the CEF effect. The analytical result of the CEF effect shows that this compound has a singlet ground state and that the CEF energy in 4f electrons from the ground state to the first excited state is 43 K. The Fermi surfaces and the cyclotron effective masses have been investigated by means of de Haas-van Alphen effect. It is found that the Fermi surfaces of PrNi 2 Al 5 are almost the same as those of LaNi 2 Al 5 .

A complete set of the 195Pt Knight-shift (KS) data on the superconducting (SC) state in UPt3 identified the spin structure of the Cooper pair corresponding to the multiple SC phases. UPt3 was acclaimed as the first odd-parity superconductor including a non-unitary pairing state characterized by the two-component d vector like d b + i d c at low T and low H [H. Tou et al., Phys. Rev. Lett. 77 (1996) 1374; 80 (1998) 3129]. We have shed further light on these novel results through a comparison with the singlet even-parity anisotropic superconductors CeCu2Si2 and UPd2Al3. In the singlet pairing state, the fractional decrease in KS below T c , δ K obs is independent of the crystal direction. We have found that δχobs=(NAμB/Ahf)δKobs where Ahf is the hyperfine coupling constant, is in good agreement with spin susceptibilities χγel calculated from an enhanced electronic specific heat γel and χnmr from the quasiparticle Korringa relation T1TKs2=const. This gives direct evidence that the χs of heavy quasiparticles in CeCu2Si2 and UPd2Al3 is rather isotropic and decreases to zero as T→0 due to the Cooper-pair formation. On the other hand in UPt3, the δχobsb,cs along the b- and c-axis in the non-unitary-pairing state (B phase) are two orders of magnitude smaller than χγel and χnmr. These anomalously small values for δχobsb,cs may suggest either that the spin degree of freedom in the B phase is not perfectly locked to the a-axis or that χs is not enhanced although γel is. The latter is theoretically pointed out by Ikeda and Miyake [J. Phys. Soc. Japan 66 (1997) 3714] to be possible if 5f electrons in the non-Kramerse singlet ground state for 5f2 are hybridized with conduction electrons. We need further effort towards coherent understanding of a microscopic mechanism leading to the occurrence of the odd-parity superconductivity in UPt3.

We have performed transport and susceptibility measurements on single-crystal CeNi2 Ge2 under high pressure and magnetic field. Under pressure a 30% decrease of the resistivity is found below 300 mK which could be due to the onset of superconductivity. Assuming this we have established the phase diagram of the superconducting phase under pressure and magnetic field. The analysis of H c 2 and the slope at Tc in comparison to a previously published report of superconductivity at ambient pressure might indicate a change in the order parameter with pressure. The normal state resistivity at ambient pressure does not show a quadratic temperature dependence. Under pressure a quadratic dependence is found and we show that the parameters of the resistivity and the susceptibility obey a simple scaling law. This scaling breaks down however when approaching the magnetic instability.

Simultaneous measurements of the magnetization M and the magnetostriction λ of a high quality single crystal of CeRu 2 Si 2 were performed at temperatures down to 70 mK in magnetic fields H up to 85 kOe, in order to test the validity of the scaling conjecture M ∼Φ[ H / H s ( P )] around the metamagnetic crossover at very low temperatures. Here H s is a characteristic field and P is the pressure. By use of a thermodynamic equality and the scaling relation, λ( H ) is calculated from the magnetization data M ( H ). For various temperatures below 4.2 K, the calculated results could be fitted to the experimental data of λ( H ) remarkably well with only the single parameter Ω ≡∂ln H s /∂ P ≈200 Mbar -1 , well confirming the scaling relation even at very low temperatures where metamagnetism becomes quite sharp. It is inferred that the metamagnetic behavior of this system is governed by a single energy scale. We have also estimated the constant-volume ( V ) magnetization curve at T =70 mK from the experimentally ...

The experiments of de Haas-van Alphen (dHvA) effect have been carried out at temperatures down to 40 mK in a magnetic dense-Kondo compound CeNi 2 Al 5 with an incommensurate magnetic structure. A complex phase diagram of the magnetic transition field versus temperature is completed. Many branches of the dHvA frequencies observed in the higher-field regions, II, III and IV, have been understood better by the branches predicted from the theoretical Fermi surfaces of nonmagnetic reference-sample LaNi 2 Al 5 rather than the theoretical ones in CeNi 2 Al 5 with 4 f electrons treated as itinerant. Branches observed in the lowest field region I are not clearly analyzed with the theoretical prediction in LaNi 2 Al 5 or CeNi 2 Al 5 . The electrons with heavy cyclotron mass are observed in the region IV; 12.4 m 0 in η branch, 11.2 m 0 in ζ branch and 9.6 m 0 in θ branch. Some pairs of parallel branches are observed due to the spin-splitting related to the magnetism, and the exchange energy Δ E is obtained; Δ E =12....

Magnetoresistance and de Haas-van Alphen measurements have been performed to investigate the Fermi-surface property of LaNi 2 Al 5 , which is a reference material of the magnetic dense-Kondo compound CeNi 2 Al 5 . Thirteen branches with the frequencies from 1.25 ×10 6 to 101 × 10 6 Oe have been observed in the angular-resolved dHvA measurements, and the magnetoresistance shows the existence of open orbits. The results are well explained by the Fermi surfaces obtained from an FLAPW band-structure calculation.

Volume effect in the temperature and field variation of the specific heat C ( T , H ) of CeRu 2 Si 2 was examined by means of detailed thermal expansion measurement performed at temperatures T ≥1.5 K in magnetic fields H ≤78 kOe. Making use of thermodynamic relations and the scaling properties that hold in the system, the specific heat C V at constant volume is estimated from experimental values of C P at constant pressure. We show that the double-peak structure in C P / T vs. H curve, recently observed by Aoki et al. across the metamagnetic critical region, still remains in the constant volume condition; it is likely to be intrinsic in origin. We have also examined the thermal expansion of the diluted system Ce 0.85 (La 0.63 Y 0.37 ) 0.15 Ru 2 Si 2 where metamagnetism is absent. Remarkable difference in the field variation of the thermal expansion coefficient between these two systems below 10 K demonstrates the existence of a low energy scale that arises from certain inter-site effect and is relevant fo...

金沢大学理工研究域数物科学系, We investigated antiferromagnetic transitions of R5lr4Si10 (R = Tb, Dy, Ho, Er) by measuring the low-temperature specific heat. The antiferromagnetic transition temperature TN is precisely determined. TN is l0.7 K for R = Tb, TN is 5.8 K for R = Dy, TN is 5.1 K for R = Ho and TN is 3.5 K for R = Er, respectively. These results suggest that the antiferromagnetic transition of the ternary rare-earth metal silicide R5lr4Si10 is dominated by the exchange interaction between R3+ ions like as the antiferromagnetic transitions in the ternary rare-earth metal compounds RCu2Ge2 (R = rare-earth metal). In addition, we report the upturn of the specific heat below 1.5 K observed for R = Tb and Ho. © 2006 Elsevier B.V. All rights reserved.

The electronic ground state of CeNiSn has been investigated by means of specific-heat measurements below 2 K in magnetic field up to 5 T using a high-quality single crystal. Unusual temperature and field dependence of specific heat reveals that the density of states of CeNiSn has a peak at ${E}_{F}$ inside the pseudogap. We claim that CeNiSn is no longer a Kondo insulator but a metal at the lowest temperature.

We report 73 Ge-nuclear-quadrupole resonance (NQR) study of heavy-fermion compound CeNi 2 Ge 2 . The temperature dependence of the 73 Ge nuclear-spin-lattice-relaxation rate 1 / T 1 indicates the development of magnetic correlations and the formation of a Fermi-liquid state at temperatures lower than T FL = 0.4 K , where 1 / T 1 T is constant. The 1 / T 1 T decrease below T c NQR = 0.1 K , whereas resistance decreases below T c onset = 0.2 K and does not become zero. These results indicate CeNi 2 Ge 2 closely locates to a superconducting quantum critical point.

We have measured the temperature dependence of the magnetic susceptibility, the electrical resistivity, the specific heat and the Hall coefficient on the pseudo-binary series Ce(Ni 1- x Pd x ) 2 Ge 2 (1.0≥ x ≥0.0). The Neel temperature decreases monotonously from 5.1 K for CePd 2 Ge 2 to 2.8 K for Ce(Ni 0.8 Pd 0.2 ) 2 Ge 2 with decreasing Pd concentration. For x ≤0.1, the ground state is paramagnetic.

Ultralow-temperature neutron scattering experiments have been carried out in order to study the antiferromagnetic ordering in the heavy fermion superconductor UPt 3 . We observed the (0.5 0 1) antiferromagnetic peak below 5 K. We found a finite spin correlation length of about 300 A above 50 mK. The peak intensity increases linearly with decreasing temperature, and is suppressed below the superconducting transition temperature of about 0.56 K. The moment size of 0.04 µ B /U was estimated from the peak intensity. These behaviors are in full agreement with results of previous studies. Surprisingly, the antiferromagnetic peak exhibits considerable narrowing below 50 mK, and a resolution-limited peak is observed below 20 mK. This is direct evidence that the antiferromagnetic long-range ordering is realized in UPt 3 at ultralow temperatures.

${}^{195}\mathrm{Pt}$ Knight shift (KS) measurements covering the superconducting multiple phases for major field ( $H$) orientations have been carried out on the high-quality single crystal ${\mathrm{UPt}}_{3}$. For $Hg5$ kOe, the KS does not change below the superconducting transition temperature ${T}_{c}$ down to 28 mK, regardless of major crystal orientations, which provides evidence that the odd-parity superconductivity with the parallel spin pairing is realized. By contrast, the KS decreases below ${T}_{c}$ for ${H}_{b}\ensuremath{\parallel}b$ axis and ${H}_{b}l5$ kOe and for ${H}_{c}\ensuremath{\parallel}c$ axis and ${H}_{c}l2.3$ kOe, whereas the KS for ${H}_{a}\ensuremath{\parallel}a$ axis is $T$ independent across ${T}_{c}$ down to ${H}_{a}\ensuremath{\sim}1.764$ kOe. These novel findings entitle ${\mathrm{UPt}}_{3}$ as the first spin-triplet odd-parity superconductor including a nonunitary pairing characterized by the two-component $\mathbf{d}$ vector like ${\mathbf{d}}_{b}+i{\mathbf{d}}_{c}$ at low $T$ and low $H$.

Kondo semiconductors are a class of strongly correlated f-electron materials whose low-energy excitations exhibit a (pseudo)gap at low temperatures. The significant difference between the pseudogap in orthorhombic CeNiSn and CeRhSb and the real gap in cubic Ce 3 Bi 4 Pt 3 and YbB 12 is highlighted by a comparison of transport properties. Low-temparature measurements of the magnetoresistance, Hall coefficient and specific heat of CeNiSn have revealed a field-induced excitation of the coherent low-carrier state. A systematic study of CeNi 1− x T x Sn ( T = Co, Cu and Pt ) has shown that the residual carriers in CeNiSn are immobilized by 1% substitution irrespective of the substitutes. Further substitution with 5% Cu induces a magnetic instability at T = 0.

We have measured the magnetoresistance at high fields up to 15 T and at low temperatures down to 0.4 K for CeNiSn with the orthorhombic structure. The longitudinal magnetoresistance (J‖‖H) is small in magnitude for the magnetic field H‖‖b- and c-axis. On the other hand, the positive magnetoresistance is found to become dominant with the decrease of temperature for H‖‖b- and c-axis in the transverse configuration (J⊥H). For H‖‖a, the magnetoresistan any current direction. These experimental results have been discussed on the basis of the cyclotron motion of the compensated carriers with closed Fermi surfaces and the reduction of the anisotropic hybridization gap.

The a-axis resistivity in UGe2 is measured in the temperature range between 0.3 and 4.5 K and in magnetic fields up to 17.5 T applied parallel to the a axis, which is the easy axis of magnetization. The T2 coefficient A of the resistivity is 0.008 μ Ω cm/K2 at zero field and is reduced by ∼50% with increasing field to 17.5 T.

The effect of magnetic field on the electronic ground state in CeNiSn has been investigated by means of specific-heat measurement in magnetic fields µ 0 H up to 14 T. A high-quality single crystal allows us to observe a marked field effect on specific heat in the temperature range from 2 to 25 K. The ground state is discussed in terms of a pseudo-gapped density of states in the Kondo resonance band with residual states at the Fermi level inducing the Zeeman splitting.

Equilibrium magnetization {ital M}{sub eq} of the superconducting mixed state of UPt{sub 3}has been measured as a function of field. At low temperatures, the discontinuity of {ital dM}{sub eq}/{ital dH} at the upper critical field {ital H}{sub {ital c}2} exhibits marked anisotropy between the two principal directions of the hexagonal crystal, being indiscernibly small for {ital H}{perpendicular}{ital c}, where the normal state paramagnetic susceptibility is largest. The results are not simply explained by the effective mass anisotropy nor by the ordinary paramagnetic effect of a spin-singlet pairing; they are rather in favor of an odd-parity pairing with an appreciable anisotropy in the pair-spin correlation. {copyright} {ital 1996 The American Physical Society.}

The temperature dependence of the {sup 195}Pt Knight shift, {ital K}, for the high quality single crystal UPt{sub 3} has been measured down to {ital T}=28 mK in applied magnetic fields parallel and perpendicular to the hexagonal {ital c} axis. No change of {ital K}{close_quote}s has been found across the superconducting transition temperature {ital T}{sub {ital c}} down to 28mK regardless of the crystal directions and independent of the superconducting multiphases. It is demonstrated that UPt{sub 3} is the odd-parity superconductor with {ital parallel} {ital spin} {ital pairing} following the direction of the magnetic field in a range of 4.4{endash}15.6kOe without an appreciable pinning of the order parameter to the lattice. {copyright} {ital 1996 The American Physical Society.}

We have found that the semiconductor-like increase in resistivity previously reported on CeNiSn and CeRhSb below about 8 K is suppressed with decreasing impurity concentration in single-crystalline samples. Nevertheless, the absolute values of the Hall coefficient strongly increase as temperature decreases. Therefore, we interpret the metallic behaviour found in the a -axis resistivity of a purified crystal of CeNiSn as a consequence of the significant increase of relaxation time of carriers. Even for the purified crystal, the residual γ value is 40 mJ/K 2 mol at 0.03 K. These results suggest that the energy gap is closed along the a -axis and that residual carriers are strongly localized in the presence of impurities.

We have measured the magnetoresistance of the orthorhombic CeNiSn at high fields up to 15 T and at low temperatures down to 0.4 K. The positive magnetoresistance is found to become dominant with the decrease of temperature for the magnetic field H applied along the b - and c -axes in the transverse configuration between the current J and the field H ( J ⊥ H ). On the other hand, the longitudinal magnetoresistance ( J ∥ H ) is small in magnitude for H ∥ b and c . For H ∥ a , the magnetoresistance is negative for any current direction. These experimental results have been discussed on the basis of the cyclotron motion of the compensated carriers with closed Fermi surfaces and the reduction of the anisotropic hybridization gap.

We have performed an extensive dHvA effect study of CeRu 2 Si 2 to gain more insight into the nature of the metamagnetic transition. The angular dependence of the dHvA frequencies confirms the transition of the Fermi surfaces from those of the itinerant f electron below the metamagnetic transition field ( H m ) to those of the localized f electron above H m . The field dependence of the frequencies and effective masses are measured for all the frequencies observed with fields parallel to [001]. A waveform analysis suggests that the Fermi surfaces of the up and down spin electrons are similar in size, whereas the effective masses are significantly different. The amplitudes of the dHvA oscillations and their field dependence are anomalous above H m , implying that the dHvA oscillations above H m may possibly come from a state which is not well developed near H m .

Several single crystals of CeNiSn and CeNi 0.95 T 0.05 Sn (T=Co and Cu) were grown and characterized by metallographic examination, electron-probe microanalysis and the measurements of resistivity, magnetoresistance, magnetic susceptibility and specific heat. Below 10 K, the semiconductor-like behavior found for dirty or substituted crystals is suppressed with decreasing impurities. For a crystal purified by the solid-state electrotransport technique, the resistivity along the orthorhombic a axis is metallic with the T 2 dependence, whereas those along the b and c axes increase below 3 K and pass through weak maxima at 0.8 K. These results suggest that the ground state of CeNiSn is not semiconducting but semimetallic with a pseudogap which closes along the a axis.

We have done the transverse magnetoresistance and the de Haas-van Alphen (dHvA) experiments in UPt 3 . The magnetoresistance increases in the whole field direction. UPt 3 is thus a compensated metal, possessing no open orbits. As for the dHvA experiment, we have observed at least three new branches. One of them is in the basal plane and the others are around the [0001] direction. The branches with dHvA frequencies of 2.7×10 7 Oe and 4.9×10 7 Oe in the field along [0001] possess large masses of 40–50 m 0 . These results have been discussed on the basis of the 5 f -itinerant Fermi surface model.

We have measured the magnetoresistance and the de Haas-van Alphen effect of YRu 2 Si 2 . The Fermi surface and cyclotron mass of YRu 2 Si 2 are compared to those of LaRu 2 Si 2 and LaRu 2 Ge 2 . Main hole Fermi surfaces of the three compounds are similar and ellipsoidal in shape, which occupy about half of the Brillouin zone. The small hole Fermi surface with a shape of rugby ball is one in number for YRu 2 Si 2 , while three for LaRu 2 Si 2 and LaRu 2 Ge 2 . A cylindrical Fermi surface and a multiply-connected Fermi surface exist for YRu 2 Si 2 , while there exists a doughnut like electron Fermi surface for LaRu 2 Si 2 and LaRu 2 Ge 2 . The cyclotron masses of YRu 2 Si 2 are about 50% and 10% larger than those of LaRu 2 Si 2 and LaRu 2 Ge 2 , respectively.

Metamagnetic transition of the heavy-electron compound ${\mathrm{CeRu}}_{2}$${\mathrm{Si}}_{2}$ has been examined on high-purity single crystals by means of a static magnetization measurement at very low temperatures down to 90 mK. No hysteresis is observed in the magnetization process. The peak value of the differential susceptibility at the metamagnetic field ${\mathit{B}}_{\mathit{M}}$\ensuremath{\sim}7.7 T follows a simple ${\mathit{T}}^{2}$ law below T\ensuremath{\sim}0.5 K, and saturates to a finite value 1.88${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/T Ce as T\ensuremath{\rightarrow}0. From these results for two single crystals with slightly different quality, we have confirmed the nonexistence of a first-order phase transition at ${\mathit{B}}_{\mathit{M}}$ in the clean limit of this system. The itinerant nature of the 4f electrons is most likely preserved in the magnetized state at B\ensuremath{\ge}${\mathit{B}}_{\mathit{M}}$.

Magnetization curves of UPt 3 along the c-axis were measured at low temperatures down to 80 mK. Below 350 mK a peak of the irreversible magnetization was found just below the superconducting upper critical field H c 2 . However, the peak disappeared above 390 mK, which is much lower than the superconducting critical temperature of 580 mK, suggesting an unconventional mechanism of the flux pinning near H c 2 . No distinct anomaly was observed in the magnetization curves at the phase transition between B and C superconducting phases.

The transverse magnetoresistance and de Haas-van Alphen (dHvA) effect in ferromagnetic RENi (RE: Pr, Nd and Sm) have been studied in fields up to 120 kOe and at temperatures down to 1.3 K. It was found that the Fermi surfaces of the three compounds contain an open surface along the b axis as in a non magnetic LaNi. On the other hand, the c -directional open surface was not found in PrNi and NdNi, being different from LaNi. Many dHvA frequency branches with the frequencies range of 2MG to 50MG were found. These branches show that the Fermi surfaces of these compounds are altered from that of LaNi by a relatively large spin splitting of the conduction band.

We have measured specific heat and electrical resistivity of Ce(Ni1−xPdx)2Ge2 (x=0.09 and 0.12) single crystals with antiferromagnetic ground state. For x∼0.12 crystal, there is no obvious rise in the electrical resistivity around the Neel temperature TN. This antiferromagnetic ordering might be understood as the itinerant antiferromagnetism of heavy-quasiparticles without the gapping behavior.

We report 101Ru NQR studies in substituted systems of a non-magnetic heavy fermion compound CeRu2Si2, Ce1−xLaxRu2Si2 (x=0.05, 0.08) and CeRu2(Si1−zGez)2 (z=0.05, 0.078). The Kondo temperature TK and the characteristic temperature of the Fermi liquid TFL, estimated from the 101Ru nuclear spin–lattice relaxation rate 1/T1, decrease with increasing x or z. A magnetic ordering is observed for z=0.078. The SCR theory is applied for an interpretation of the T-dependence in 1/T1, and it is suggested that the magnetic to non-magnetic transition against x or z may occur as a first-order type in these systems without passing through the quantum critical point (TN→0).

We investigated antiferromagnetic transitions of R 5 lr 4 Si 10 (R = Tb, Dy, Ho, Er) by measuring the low-temperature specific heat. The antiferromagnetic transition temperature T N is precisely determined. T N is l0.7 K for R = Tb, T N is 5.8 K for R = Dy, T N is 5.1 K for R = Ho and T N is 3.5 K for R = Er, respectively. These results suggest that the antiferromagnetic transition of the ternary rare-earth metal silicide R 5 lr 4 Si 10 is dominated by the exchange interaction between R 3+ ions like as the antiferromagnetic transitions in the ternary rare-earth metal compounds RCu 2 Ge 2 (R = rare-earth metal). In addition, we report the upturn of the specific heat below 1.5 K observed for R = Tb and Ho.

We report measurements of the magnetic susceptibility, specific heat, magnetoresistance, Hall effect, and Fermi surface in SmCu{sub 6}. The susceptibility follows the Van Vleck form for Sm{sup 3+} near room temperature and shows two antiferromagnetic phase transitions at 9.6 and 5.2 K. The specific heat implies a quartet ground state for the crystal-field-split {ital J}=5/2 angular momentum state. Magnetoresistance indicates that SmCu{sub 6} contains both electron and hole carriers but is uncompensated. de Haas--van Alphen measurements show that the Fermi surface in the antiferromagnetic state consists of a network of cylinders oriented 30{degree} from the {ital b} and {ital c} axes.

We report measurements of resistivity $\ensuremath{\rho}$ in ${\mathrm{UGe}}_{2}$ at temperatures $T$ down to $0.3\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, pressures $P$ up to $19.8\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$, and magnetic fields ${B}_{\mathrm{appl}}$ up to $17.5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ applied along the magnetic easy $a$ axis. The coefficient $A$ of the ${T}^{2}$ term of $\ensuremath{\rho}(T)$ is determined as a function of ${B}_{\mathrm{appl}}$ and $P$. In the large-moment ferromagnetic phase (the $\mathrm{low}\text{\ensuremath{-}}P∕\mathrm{high}\text{\ensuremath{-}}{B}_{\mathrm{appl}}$ phase), $A$ is found to be a function of the single parameter $({B}_{\mathrm{appl}}\ensuremath{-}{B}_{x})$ and approximately obeys a power law $A\ensuremath{\propto}({B}_{\mathrm{appl}}\ensuremath{-}{B}_{x}{)}^{\ensuremath{-}1∕2}$, where ${B}_{x}$ is the transition field from the small- to the large-moment ferromagnetic phase. The $T$ dependence of $\ensuremath{\rho}$ at fields just above ${B}_{x}$ suggests a contribution to $\ensuremath{\rho}$ from excitations with a gapped spectrum.

We present evidence for unconventional superconducting fluctuations in a heavy-fermion compound CeNi$_2$Ge$_2$. The temperature dependence of the $^{73}$Ge nuclear-spin-lattice-relaxation rate $1/T_1$ indicates the development of magnetic correlations and the formation of a Fermi-liquid state at temperatures lower than $T_{\rm FL}=0.4$ K, where $1/T_1T$ is constant. The resistance and $1/T_1T$ measured on an as-grown sample decrease below $T_{\rm c}^{\rm onset} = 0.2$ K and $T_{\rm c}^{\rm NQR} = 0.1$ K, respectively; these are indicative of the onset of superconductivity. However, after annealing the sample to improve its quality, these superconducting signatures disappear. These results are consistent with the emergence of unconventional superconducting fluctuations in close proximity to a quantum critical point from the superconducting to the normal phase in CeNi$_2$Ge$_2$., 4pages,5figures,to appear in J. Phys. Soc. Jpn

The electrical resistivity and the lattice parameters of the tetragonal heavy-fermion compound CeNi2Ge2 with ThCr2Si2 type of structure have been investigated under high pressure. At room temperatures, the compression curve of an unit-cell volume up to 70 kbar is well fitted to Murnaghan equation of state. In the electrical resistivity at low temperatures, a gradual depression of the Fermi-liquid AT2 term with increasing pressure is observed. From these results, the Gruneisen parameter of the characteristic energy of the Fermi-liquid ground state is determined to be 90.

The effects of the normal state paramagnetism on the superconductivity of UPt3 and URu2Si2 were investigated by means of static magnetization measurements. While the upper critical field of URu2Si2 seems to be paramagnetically suppressed, no clear spin reduction is observed in the magnetization curves. The paramagnetic polarization in UPt3 for H⊥c(H‖c) is as large as (slightly suppressed below) the normal-state value, although the normal state spin susceptibility is considered to be largest for H⊥c. The results of UPt3 point to an odd-parity pairing with a discernible anisotropy in the pair-spin state.

We have studied the temperature dependence of the electrical resistivity, the magnetic susceptibility and the high-field magnetization of CeNi 2 Ge 2 . Quadratic temperature dependence of the resistivity is observed below 0.7 K. The susceptibility exhibits a broad maximum at 28 K. Magnetization shows metamagnetic behavior at H M ∼42 T as in CeRu 2 Si 2 . These results indicate that CeNi 2 Ge 2 is a new heavy-fermion compound showing the metamagnetic behavior in the nonmagnetic ground state.

We have done de Haas—van Alphen (dHvA) experiments in UPt 3 and have observed at least three new branches. One of them is in the basal plane and the others are around the [0001] direction. The branch with a dHvA frequency of 2.7 × 10 7 Oe in the field along [0001] possesses a large mass of 40 m o .

We report an extensive study of the angular dependence of the de Haas-van Alphen frequencies for the field directions in the (0 1 0) and (0 0 1) planes, and the field dependence of the effective masses and frequencies below and above the metamagnetic transition field (Hm) in CeRu2Si2. The present study confirms our previous conclusion that the Fermi surfaces change from those of itinerant f electrons below Hm to those of localized f electons above Hm.

We have measured the thermopower along the three crystallographic axes of single crystals at 1.3 K and 4.2 K under a magnetic field up to 10 T applied perpendicularly to the direction of the temperature gradient. There are six cases altogether for the direction of the magnetic field relative to the temperature gradient along the crystal axis. The value of the thermopower was found to decrease drastically as the increase of the magnetic field applied in parallel only to the a-axis, the axis having the largest magnetic susceptibility, inferring the destruction of the band gap due to the magnetic field.

Thermopower of Pr 3 Co, Nd 3 Co and Sm 3 Co are measured in the temperature range from 4.2 K to 280 K. The thermopowers in the high temperature region show negative values for La 3 Co and Nd 3 Co and a positive value for Sm 3 Co. However, that of Pr 3 Co shows a small negative constant value. These behaviors are considered in relation to the density of state of Co in R 3 Co at the Fermi energy on the basis of Mott's equation of the thermopower.

The ac susceptibility and de Haas\char21{}van Alphen (dHvA) effect in ${\mathrm{UGe}}_{2}$ are measured at pressures P up to 17.7 kbar for the magnetic field B parallel to the a axis, which is the easy axis of magnetization. Two anomalies are observed at ${B}_{x}(P)$ and ${B}_{m}(P)$${(B}_{x}g{B}_{m}$ at any $P),$ and the $P\ensuremath{-}B$ phase diagram is presented. The Fermi surface and quasiparticle mass are found to vary smoothly with pressure up to 17.7 kbar unless the phase boundary ${B}_{x}(P)$ is crossed. The observed dHvA frequencies may be grouped into three according to their pressure dependences, which are largely positive, nearly constant, or negative. It is suggested that the quasiparticle mass moderately increases as the boundary ${B}_{x}(P)$ is approached. DHvA effect measurements are also performed across the boundary at 16.8 kbar.

We have measured the magnetoresistance and de Haas-van Alphen effect in LaNi and CeNi. The Fermi surface of CeNi is found to be similar to the one of LaNi, while the cyclotron masses of CeNi are about ten times heavier than those of LaNi.

A GdNi single crystal has been prepared by the Czochralski method and studied by measuring the magnetization, electrical resistivity and thermal expansion. The ferromagnetic ordering below T C =69 K has been confirmed. The saturated magnetization at 2 K was found to be identical (7.2 μ B /f.u.) along all the three principal crystallographic directions. This result is in agreement with theoretical calculations, which yield magnetic moment of 7.0 μ B /f.u. for Gd 3+ ion and 0.18 μ B /f.u. for conduction electrons with magnetic moment of the same direction as the Gd moment. An anomalous spontaneous magnetostriction is dominating the thermal expansion behavior below T C . In particular, we have observed a large contraction in the c -direction and a smaller expansion in the a and b directions (nearly identical). The unit cell volume expands below T C (Δ V / V =8×10 −4 ). The observed anisotropy of the magnetostriction in GdNi is attributed to anisotropic magnetoelastic coupling.

We have performed resistivity measurements on UGe 2 at low temperatures (0.3 K⩽ T ) in a wide range of magnetic fields ( B appl ⩽17.5 T) and pressure ( P ⩽19.8 kbar). The residual resistivity and the T 2 coeeficient of resistivity are given as functions of B appl and P . Their changes across magnetic phases are discussed.