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195Pt-NMR measurements for H ∥ c in the vicinity of the upper critical field \(H_{\text{c2}}^{\| c}\) have been carried out on the heavy-fermion superconductor UPt3. The 195Pt NMR line does not cha...

We report the de Haas–van Alphen (dHvA) effect for noncentrosymmetric Yb4Sb3. The theoretically expected electronic structure consists of pairs of split Fermi surfaces due to the antisymmetric spin...

We report the de Haas–van Alphen effect study on the evolution of spin dependence of the effective mass in CeIn 3 and CeRu 2 (Si 1- x Ge x ) 2 by using physical and chemical pressures to control the relative strengths ot the Kondo effect and the RKKY interaction.

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.

Systematic neutron scattering experiments were carried out in order to reveal the crystal and magnetic structure as well as the localized character of the uranium 5 f electrons in a ternary metalli...

We have studied the Fermi surface properties of CeRu 2 Si 2 below and above the metamagnetic transition (MT) under high pressures. The frequencies of the dHvA oscillations change considerably with pressure both below and above the MT. The pressure coefficient of the frequencies are larger than those of normal metals by more than ten times. The sign and value of the pressure coefficient depend on the dHvA frequency or the orbit. Below the MT the effective masses decrease with increasing pressure, while that above the MT is found to slightly increase. The dHvA oscillations can be traced through the MT at high pressures and it is found that the Fermi surface changes from that of the itinerant f electron to another Fermi surface which is similar to that of the localized f electron in a field range much narrower than that of the MT width in the magnetization. An analysis based on the pressure effect of the Fermi surface indicates that the Fermi surface remains unchanged when the filed approaches the MT field (...

The de Haas-van Alphen (dHvA) effect has been investigated on high-quality single crystals of FeP in a double helical magnetic state with a 5 c period in the magnetic fields up to 14 T and at tempe...

The acoustic de Haas-van Alphen (dHvA) effect and temperature dependence of the transverse mode ( C 11 - C 12 )/2 have been measured in a layered Perovskite superconductor Sr 2 RuO 4 with T c * = 1...

Magnetization and resistivity were measured as functions of temperature and magnetic field on two single crystals of CaB 6 and three of (Ca 0.995 La 0.005 )B 6 . One of the doped crystals exhibited...

We have succeeded in growing the single crystal of a new ternary intermetallic uranium compound U 3 Pd 20 Si 6 . It crystallizes in the Cr 23 C 6 -type cubic structure and the uranium ions are located on two different crystallographic sites. Two sucessive magnetic phase transitions are found at 19 K and 2 K in the electrical resistivity, specific heat and magnetic susceptibility measurements. These are attributed to antiferromagnetic and ferromagnetic orderings, respectively. The magnetic susceptibility obeys the Curie-Weiss law above about 50 K with the effective moment 3.30 µ B /U and the magnetic entropy at 19 K is about R ln 3 per uranium ion. These results indicate that the 5 f electrons in U 3 Pd 20 Si 6 are likely to be localized. We discuss the magnetic properties of U 3 Pd 20 Si 6 in comparison with those of R 3 Pd 20 X 6 (R=rare earth: X= Si, Ge).

We present a report on crystalline-electric-field effects observed in the electrical resistivity and the specific heat of Ce 3 Pd 20 Ge 6 , which are discussed within an energy level scheme of the Γ 8 ground state and the Γ 7 excited state at 50 K for both inequivalent crystallographic sites of Ce atom. The third-order magnetic susceptibility was deduced from the magnetization measurement in the paramagnetic phase of a single-crystalline sample in magnetic fields applied along [0 0 1] and [1 1 1]. In order to explain the temperature dependence of the third-order magnetic susceptibility along [0 0 1], a positive total quadrupolar pair interaction constant of 22 mK is required in addition to a small antiferromagnetic exchange interaction, thereby suggesting ferroquadrupolar ordering with the Γ 3 symmetry in this compound.

We have performed the de Haas-van Alphen (dHvA) experiments in UPt 3 . A new branch has been observed in a relatively wide angle region. It has a large cyclotron effective mass of 80 m 0 and the dHvA frequency is 5.66 ×10 7 Oe for the field along the [0001] direction. The new branch most likely corresponds to the main electron Fermi surface in the 37th band of the 5 f -itinerant band model.

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.

Josephson critical current I c between a single crystal UPt 3 and Al has been measured for a corner junction on the UPt 3 faces perpendicular to the a [11 2 0] and b [10 1 0] axes. The magnetic field dependence of I c has shown a global maximum at zero magnetic field like the junctions on a single face. We have not observed a behavior indicating the phase shift of the order parameter between the a - and b -axis directions thus far.

We have grown single crystals of superconductor CeRu 2 by a zone melting method, on which we have measured the lower and upper superconducting critical fields. They are estimated as 250-400 Oe and 74 kOe at 0 K, respectively. The upper critical field H c2 is slightly anisotropic, 64.8 kOe for the field along the direction and 65.6 kOe for at 1.5 K. We have also observed a characteristic feature in the superconducting mixed state.

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 observed the de Haas-van Alphen oscillation in LaAg and CeAg. Four kinds of closed Fermi surfaces are detected in LaAg, which are in good agreement with the results of band calculations. In CeAg, each Fermi surface is split into two Fermi surfaces with the up- and down-spin states due to the ferromagnetic exchange interaction. The cyclotron mass of CeAg is not very large, which is only by 40% larger than the corresponding mass of LaAg.

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.

We have observed the de Haas-van Alphen oscillation of the antiferromagnetic compound NdPb 3 . Main Fermi surfaces consist of four closed ones, which are in good agreement with the results of band calculations based on the FLAPW method for the non-magnetic reference compound LuPb 3 . The cyclotron effective masses are in the range of 0.4 m 0 to 3 m 0 .

We have successfully grown a high-quality single crystal of ThRu2Si2 with the residual resistivity ratio (RRR) of 120, which is a reference compound to the heavy-fermion systems CeRu2Si2 and URu2Si2 crystallizing in the tetragonal ThCr2Si2-type structure, and observed the quantum oscillations (de Haas–van Alphen effect). The result is compared with the Fermi surfaces of CeRu2Si2 and URu2Si2 as well as the band structure calculations. The main features of Fermi surface topology of ThRu2Si2 are similar to those of the heavy-fermion compound CeRu2Si2, indicating that the 4f electron in CeRu2Si2 contributes to the conduction band. On the other hand, the Fermi surfaces of ThRu2Si2 significantly differ from those obtained for URu2Si2, suggesting the itinerant nature of 5f electrons rather than the conventionally assumed localized 5f2 configuration.

We show that superconductivity observed in the antiferromagnetic state of CeIrSi3, a pressure-induced heavy fermion superconductor, is mainly due to a surface layer induced by mechanical polishing. The superconducting reduction of the electrical resistivity in the antiferromagnetic state strongly depends on the strength of the applied electrical current and dissipates after a heat treatment. These results indicate that mechanical polishing causes an inhomogeneous distortion on the surface of the sample and locally produces a high-pressure region in which the bulk superconductivity arises.

We report the specific heat and ac magnetic susceptibility of noncentrosymmetric superconductor LaRhSi3. A first-order superconducting transition is observed in specific heat C under different magnetic field values. The C(T) values in zero-field-cooling and field-cooling processes become different at a magnetic field between 20 and 130 Oe. These results suggest that conversion from type-I to type-II/1 superconductivity is realized in LaRhSi3. The ac susceptibility indicates that surface superconductivity with an extremely high limiting field occurs probably due to the conversion temperature.

We report on high-precision magnetization measurements on the non-Kramers cubic compound Pr 3 Pd 20 Ge 6 for temperatures down to ∼80 mK, in fields applied parallel to the [100] and [110] directions up to 8.5 T. Multistep-like structures of the magnetization curves are found below about 1 K for both the field directions. Temperature variations of the magnetic susceptibility show no tendency to saturate down to 80 mK, implying that the crystalline-electric-field (CEF) lowest state of 4f electrons for at least one of the Pr sites is the magnetic triplet Γ 5 . No significant anomaly is observed at 0.26 K, where quadrupole order is suggested from ultrasonic sound velocity measurements. An application of a simple CEF model is discussed.

We have performed the de Haas–van Alphen (dHvA) experiment to elucidate the Fermi surface (FS) property of the typical localized 5 f -electron system of UPd 3 using a high-quality sample (RRR = 100). Many dHvA branches are newly observed. The FS topology is discussed comparing the angular dependence of the dHvA frequency and the two different band models. An anomaly due to the quadrupolar or magnetic interaction can not be found in the observed dHvA signal as well as the ac susceptibility up to 17.5 T.

We performed angle-resolved photoemission spectroscopy (ARPES) on Ca 1- x La x B 6 ( x =0.01) to study the electronic structure and the origin of the anomalous high-temperature ferromagnetism. We found a large energy gap of about 1 eV at the Fermi level at the X point in the Brillouin zone in contrast to the LDA band calculation, which has predicted the semimetallic nature of CaB 6 with a small overlap of an electron and a hole pocket at the X point. The band structure determined by ARPES shows a good agreement with the GW band calculation which predicts the semiconductive character. The present ARPES results request reexamination of the excitonic-insulator model based on a small overlap of two bands at the X point to explain the ferromagnetism in Ca 1- x La x B 6 .

We have performed nuclear quadrupole resonance and nuclear magnetic resonance measurements on UCoAl with strong Ising-type anisotropy under $b$- and $c$-axes uniaxial pressure. In the $b$-axis uniaxial pressure ($P_{\parallel b}$) measurement, we observed an increase in the metamagnetic transition field with increasing $P_{\parallel b}$. In the $c$-axis uniaxial pressure ($P_{\parallel c}$) measurement, on the other hand, we observed a ferromagnetic transition in zero magnetic field along the $c$-axis above $P_{\parallel c}$ = 0.08 GPa. The anomaly of the nuclear spin-lattice relaxation rate divided by the temperature $\left[ (T_1 T)^{-1} \right]$ at $T$ = 20 K is suppressed by $P_{\parallel b}$ and slightly enhanced by $P_{\parallel c}$. The anisotropic uniaxial pressure response indicates that uniaxial pressure is a good parameter for tuning the Ising magnetism in UCoAl., Comment: 6 pages, 9 figures

This article describes the Fermi surface properties of CeRu2Si2 and its alloy systems CeRu2(SixGe1−x)2 and CexLa1−xRu2Si2 studied by the de Haas–van Alphen (dHvA) effect. We pay particular attention to how the Fermi surface properties and the f electron state change with magnetic properties, in particular how they change associated with metamagnetic transition and quantum phase transition. After summarizing the important physical properties of CeRu2Si2, we present the magnetic phase diagrams of CeRu2(SixGe1−x)2 and CexLa1−xRu2Si2 as a function of temperature, magnetic field and concentration x. From the characteristic features of the magnetic phase diagram, we argue that the ferromagnetic interaction in addition to the antiferromagnetic interaction and the Kondo effect is responsible for the magnetic properties and that the metamagnetic transitions in these systems are relevant to the ferromagnetic interaction. We summarize the Fermi surface properties of CeRu2Si2 in fields below the metamagnetic transiti...

We represent our recent advances on the study of the gap symmetry in UPt3 by thermal conductivity tensors κij (i, j = x, y, z). The field-angle-resolved thermal conductivity κzz shows spontaneous twofold symmetry breaking in the gap function for the high-field C-phase, indicating that the pairing symmetry of UPt3 belongs to an E1u representation in the f-wave category. We also demonstrate that the proposed pairing symmetry is compatible with most of the experimental results reported until now.

We have studied the pressure dependence of the de Haas–van Alphen (dHvA) frequencies in the lowest magnetic phase AF of CeSb. It is found that the dHvA frequencies change discontinuously between ambient pressure and 2.6 kbar, implying that a magnetic phase transition takes place between these pressures.

We have investigated the field-angle variation of the specific heat C(H, phi, theta) of the heavy-fermion superconductor UPt3 at low temperatures T down to 50 mK, where phi and theta denote the azimuthal and polar angles of the magnetic field H, respectively. For T = 88 mK, C(H, theta=90) increases proportionally to H^{1/2} up to nearly the upper critical field Hc2, indicating the presence of line nodes. By contrast, C(H, theta=0) deviates upward from the H^{1/2} dependence for (H/Hc2)^{1/2} > 0.5. This behavior can be related to the suppression of Hc2 along the c direction, whose origin has not been resolved yet. Our data show that the unusual Hc2 limit becomes marked only when theta is smaller than 30. In order to explore the possible vertical line nodes in the gap structure, we measured the phi dependence of C in wide T and H ranges. However, we did not observe any in-plane angular oscillation of C within the accuracy of dC/C~0.5%. This result implies that field-induced excitations of the heavy quasiparticles occur isotropically with respect to phi, which is apparently contrary to the recent finding of a twofold thermal-conductivity oscillation., 6 pages, 5 figures, Selected for an Editors' Choice

The Josephson critical current I c between a single-crystal UPt 3 and Al has been measured for the junctions on the UPt 3 surface perpendicular to the hexagonal a [11\bar20], b [10\bar10], and c [0001] axes. The magnetic field dependence of I c shows a Fraunhofer diffraction pattern for a current flow parallel to the c -axis, suggesting that the Josephson coupling is uniform throughout the junction. Small modifications applied to the Fraunhofer pattern have been observed for a current flow parallel to the a - and b -axes. These results contradict the E 2 u scenario for the odd-parity order parameter in UPt 3 , in which the Josephson effect is forbidden in the three directions, whereas the recently proposed E 1 u scenario permits, at least, the a - and c -axis Josephson couplings.

We report high-precision magnetic and transport measurements of ZrZn 2 and present a phase diagram as a function of pressure and magnetic field. The paramagnetic phase is found to be divided into two regions at T ≃0 by a possible electronic topological transition (i.e., a non-symmetry breaking transition) known as the Lifshitz transition, and the two regions are characterized by Fermi and non-Fermi liquid behaviors. These results strongly suggest that the non-Fermi liquid state exists as a stable phase distinguished from the Fermi liquid by the Fermi surface topology. As a possible origin of the non-Fermi liquid behavior, an antiferromagnetic fluctuation arising from the Fermi surface nesting is discussed.

We report a continuous evolution of Fermi surface properties with temperature in a dilute Kondo alloy of Ce 0.02 La 0.98 Ru 2 Si 2 via measurements of the de Haas–van Alphen (dHvA) effect. The temperature variation of resistivity in this alloy exhibits a typical impurity Kondo behavior, i.e., the resistivity increases with decreasing temperature proportionally to -log T and becomes nearly constant below about 0.3 K. The Kondo temperature of this alloy is estimated to be about 1.3 K. The frequency of the dHvA oscillation from the main hole surface decreases with decreasing temperature implying that the hole surface shrinks with decreasing temperature. The temperature dependence of the frequency change is found to be similar to that of resistivity. The temperature dependence of this dHvA oscillation amplitude deviates largely from that expected from the Lifshitz–Kosevich formula conventionally employed to determine the effective mass from the temperature dependence. By assuming that the scattering of the co...

We have performed an extensive study on the electronic transport properties of Ce x La 1- x Ru 2 Si 2 . At zero field or under the fields parallel to the hard axis of magnetization, the residual resistivity, magnetoresistivity and Hall resistivity are found to be most enhanced around x = 0.85 in the antiferromagnetic state. On the other hand, the high magnetic field along the easy axis is effective to suppress the enhancement. The coherence temperature derived from the temperature variation of Hall coefficient becomes equal to the antiferromagnetic transition temperature at x = 0.85, indicating that the competition between the coherence of the Kondo singlet and the long range magnetic order is responsible for the enhancement. The competition is likely to affect also the magnetic properties in the antiferromagnetic state. The comparison with the de Haas–van Alphen effect measurements suggests that the enhancement is likely to be due to the increase in scattering. The present results are compared with the t...

We report de Haas–van Alphen (dHvA) effect measurement of the intermediate-valence compound CeCoSi 3 whose crystal structure lacks space-inversion symmetry. Some dHvA frequencies of CeCoSi 3 qualitatively correspond to those of CeRhSi 3 which is a heavy-fermion antiferromagnet exhibiting pressure-induced superconductivity. We observed multiply splitting dHvA frequencies and attributed them to the magnetic breakdown between two separated Fermi surfaces due to the antisymmetric spin–orbit coupling (ASOC). Strikingly, the cyclotron effective masses of the separated Fermi surfaces are largely different, indicating that the mass enhancement depends on the spin direction. The evaluated ASOC energy of CeCoSi 3 is less than that of LaCoGe 3 , which is probably characteristic of a heavy-fermion band with an itinerant f -electron.

We report the magnetic, transport and de Haas–van Alphen (dHvA) effect measurements to investigate the evolutions of metamagnetic behavior and electronic structure with Ge concentration x in CeRu 2 (Si 1- x Ge x ) 2 . With decreasing x , the ground state changes from ferromagnetic state to antiferromagnetic state at x a = 0.58, then to paramagnetic state at x c = 0.065. When a magnetic field is applied parallel to the [001] direction, first order metamagnetic transition takes place in the anitferromagnetic state and it changes to metamagnetic crossover in the paramagnetic state at x c . It is also found that the metamagnetic behavior as well as the magnetic phase diagram qualitatively change at x b = 0.29. The transport and dHvA effect measurements have been performed with fields applied in the (001) plane for which no metamagnetic transition takes place. With decreasing x , the magnitudes of the residual resistivity at 0.5 K, the coefficient A of T 2 term in the temperature dependence of resistivity, the...

The thermoelectric power S and the electrical resistivity ρ of a single-crystalline CeIrSi 3 with the non-centrosymmetric tetragonal crystal structure were measured under pressure up to 2.72 GPa in the temperature range from 1.5 to 300 K. The electronic state of CeIrSi 3 is turned from the antiferromagnetic state to superconducting state as a function of pressure. S exhibits a large positive value up to about 52 µV/K, which is characteristic of heavy-fermion systems. S shows a maximum in its temperature dependence due to the Kondo effect and its maximum temperature T S ,max gradually moves to higher temperatures from about 100 K (at ambient pressure) to about 120 K (at 2.72 GPa) by applying the pressure. We also observed the antiferromagnetic transition as the kink in the temperature dependence of S at pressure up to 2.12 GPa.

We report the de Haas–van Alphen (dHvA) effect study on Pr 0.03 La 0.97 Pb 3 where the non-Fermi liquid behavior is observed in the specific heat and resistivity measurements. The dHvA frequencies and the effective masses do not change appreciably from those of LaPb 3 within the experimental errors. The effective masses are nearly constant from the high field range of the Fermi liquid state down to the low field range where the non-Fermi liquid behavior is observed. On the other hand, large phase shifts with temperature are observed in the dHvA oscillations. These observations indicate that the anomaly of the specific heat may not be related to that of electronic specific heat but there is a significant interaction between the conduction electrons and the f electron.

Angle-resolved photoelectron spectroscopy was measured in the Ce 3 d →4 f resonance energy region for the paramagnetic state of CeRu 2 Si 2 , Ce 0.84 La 0.16 Ru 2 Si 2 , and LaRu 2 Si 2 to investigate a variation of band structures around the quantum critical point (QCP). While the results clearly demonstrate the difference of the band structures between CeRu 2 Si 2 and LaRu 2 Si 2 , the observed band structures of CeRu 2 Si 2 and Ce 0.84 La 0.16 Ru 2 Si 2 resemble each other. The results indicate that the Ce 4 f electrons in the paramagnetic state have an itinerant character in either side of the critical composition, and Ce 1- x La x Ru 2 Si 2 near QCP is similar to CeRu 2 (Si 1- x Ge x ) 2 .

The noncentrosymmetric heavy fermion superconductor CeRhSi 3 exhibits an extremely large superconducting upper critical field B c2 for the magnetic field along the c axis. This remarkable feature is ascribed to the noncentrosymmetric (Rashba-type) crystal structure which can avoid the paramagnetic pair-breaking effect. The pressure dependence of the B c2 ( T ) curve, however, is very complicated and remains as an unresolved issue. Recently, we found a bend in the B c2 ( T ) curve which emerges at a pressure where the antiferromagnetic order disappears. Furthermore, an anomaly in the electrical resistivity in the normal state emerges above the magnetic field of the bend point. The obtained magnetic and superconducting phase diagram thus appears to have complicated structure especially in the vicinity of the pressure where the antiferromagnetic order vanishes.

We report the temperature dependence of the zero-field ac-susceptibility of CeRhSi 3 under several pressures. We have observed a clear difference between the onset temperature of superconducting transition T c onset and main shielding temperature T c main . T c main approaches T c onset with increasing pressure and merges at about 2.4 GPa at which the antiferromagnetism vanishes under zero field. In the temperatures between T c onset and T c main , the decrease of χ' is quite small while χ'' changes largely. At T c main , χ' drops and χ'' peaks sharply as those of conventional superconductors. These results imply that CeRhSi 3 has two different types of pinning state in the superconductivity and the appearance of them is probably associated with the antiferromagnetic state.

We have preformed the de Haas–van Alphen effect measurements in Ce x La 1- x Ru 2 Si 2 with magnetic fields in the (001) plane. All the oscillations corresponding to those in LaRu 2 Si 2 can be observed in low Ce concentration samples and the evolution of the Fermi surface properties with x is found to depend strongly on the Fermi surface sheet. We show that the evolution can be attributed to anisotropic hybridization of the f electron with conduction electrons and resultant delocalization of the f electron.

We report the de Haas–van Alphen (dHvA) effect studies above metamagnetic transition fields in Ce x La 1- x Ru 2 Si 2 . Three dHvA oscillations β', γ', and δ are observed for all the samples from x = 0.0 to 1.0. The frequencies and effective masses of these oscillations vary smoothly with the Ce concentration from LaRu 2 Si 2 to CeRu 2 Si 2 . The signal magnitude is reduced only by a factor of approximately 1/10 at most even in alloys with a high concentration of Ce. These behaviors are the same as those observed in the alloys of the compounds with localized f electrons, indicating that the f electron maintains localized nature above the metamagnetic transitions.

We review the normal and superconducting properties in the noncentrosymmetric heavy-fermion CeRhSi 3 . In the normal state, CeRhSi 3 exhibits the antiferromagnetic order at low temperatures (1.6 K at ambient pressure) although its Kondo temperature is much higher than the ordering temperature T N . With applying pressure P , T N initially increases and subsequently decreases. The superconductivity arises at the pressures where the antiferromagnetic transition occurs. T N does not seem to fall to zero but becomes nearly constant with further application of pressure, and then T N vs P merges with the superconducting transition temperature T c vs P at 26 kbar where T c reaches the maximum. Nearly perfect magnetic-shielding associated with the superconductivity is observed below 26 kbar, suggesting that the bulk superconductivity is realized below T N . We observe an anomaly below T c in the resistivity as well as in the ac-susceptibility. The origin of the both anomalies seem to be the same but have not been...

We have studied the crystalline electric-field effect of the noncentrosymmetric heavy-fermion antiferromagnet CeRhSi 3 by measuring the magnetic susceptibility χ( T ), specific heat C p ( T ) and inelastic neutron scattering. The 4 f level scheme determined from χ agrees with a magnetic excitation observed in the inelastic neutron spectra and the Schottky anomaly in the magnetic part of C p . Moreover, we have measured C p under various magnetic fields B up to 8 T and observed that the Neel temperature T N decreases proportionally to B 2 for B ∥ a -axis while the B dependence of T N is rather small for B ∥ c -axis. This anisotropic behavior suggests that the antiferromagnetically ordered moments lie in the tetragonal c -plane.

We report the de Haas–van Alphen (dHvA) effect measurements of the Fermi surface properties in LaB 6 , Ce x La 1- x B 6 ( x = 0.1, 0.25, 0.5, 0.75, 1.0) and Pr x La 1- x B 6 ( x = 0.25, 0.5, 0.75, 1.0) with particular attention to the spin dependence of the Fermi surface properties. The Fermi surface shape and dimension of Ce x La 1- x B 6 change considerably with Ce concentration, while those of Pr x La 1- x B 6 change very slightly up to x = 0.75, and in PrB 6 the Fermi surface splits into the up and down spin Fermi surfaces. The effective mass of Ce x La 1- x B 6 increases considerably with Ce concentration and is nearly proportional to the number of Ce ions, whereas that of Pr x La 1- x B 6 increases slightly with Pr concentration. In Ce x La 1- x B 6 the effective mass depends very strongly on field and increases divergently with decreasing field, while that of Pr x La 1- x B 6 increases slightly with decreasing field. The contribution to the dHvA signal from the conduction electrons of one spin dire...