dHvA Branches Research Articles

Electrical and Magnetic Properties of CeAu2Si2

We succeeded in growing a high-quality single-crystal of CeAu 2 Si 2 , which was previously reported to be highly sample-dependent in terms of electrical and magnetic properties. CeAu 2 Si 2 is not a simple AF1-type antiferromagnet, but reveals three antiferromagnetic transitions in a narrow temperature range from the Neel temperature T N1 =9.6 K to T N3 =8.0 K. A clear metamagnetic transition with two steps was observed at H c1 =53 kOe and H c2 =55 kOe in the magnetization curve below 5 K for the magnetic field along an antiferromagnetic easy-axis, namely, the tetragonal [001] direction, with a saturation moment of 1.53 µ B /Ce. The magnetic susceptibility and magnetization are anisotropic, which are well explained by results of crystalline electric field analyses. We also studied the de Haas–van Alphen (dHvA) effect. The detected dHvA branches are found to be consistent with those of a non-4 f reference compound such as YCu 2 Si 2 .

The de Haas–van Alphen Oscillation and Fermi Surface Properties of YCu2Si2

We have succeeded in growing a high-quality single crystal of a non-4 f reference compound YCu 2 Si 2 for a heavy-fermion superconductor CeCu 2 Si 2 , and observed the de Haas–van Alphen (dHvA) oscillation. The detected dHvA branches in YCu 2 Si 2 indicate that the Fermi surfaces are multiply connected, and the dHvA frequencies are in the range from 9×10 6 to 2×10 8 Oe. These dHvA branches are found to be well explained by the results of energy band calculations. The corresponding cyclotron masses are light, ranging from 0.4 to 1.5 m 0 , and are consistent with the electronic specific heat coefficient of 2.2 mJ/(K 2 ·mol).

Single Crystal Growth and de Haas–van Alphen Effect in Lu2Rh3Ga9 with Quasi-Two-Dimensional Electronic State

We succeeded in growing a single crystal of a layered compound Lu 2 Rh 3 Ga 9 with an Y 2 Co 3 Ga 9 -type orthorhombic crystal structure by the Ga-flux method. The lattice, positional, and thermal parameters were determined by single-crystal x-ray diffraction measurement. We also measured the electrical resistivity, specific heat, and de Haas–van Alphen (dHvA) effect. The detected dHvA branches were well explained by the results of full potential linear augmented plane-wave (LAPW) energy band calculations. The electronic state was found to be quasi-two-dimensional, indicating nearly cylindrical Fermi surfaces along the [001] direction.

Electrical Properties and dHvA Experiments in Ferromagnet Ce3Al11

High-quality single crystals of Ce 3 Al 11 with the orthorhombic crystal structure have been grown by the Al-flux method. Signatures for ferromagnetic and antiferromagnetic orderings at T C = 6.3 K and T N = 3.2 K, respectively, have been observed in the electrical resistivity. On application of pressure, the Neel temperature T N decreases rapidly and goes to zero around 3 GPa. On the other hand, the Curie temperature T C is found to be robust against pressure up to 4 GPa. Further, dHvA oscillations have been obtained for magnetic field along the [0 1 0] direction. A cyclotron mass m c * as large as 28 m 0 ( m 0 : rest mass of an electron) has been observed for one of the dHvA branches, indicating the heavy fermion nature of Ce 3 Al 11 .

Single Crystal Growth and Fermi Surface Property in ThRhIn5

We succeeded in growing a high-quality single crystal of ThRhIn 5 with the HoCoGa 5 -type tetragonal crystal structure by the In-flux method. The lattice parameters, positional parameters and thermal parameters were determined from single-crystal x-ray diffraction measurements. We also measured the electrical resistivity and de Haas–van Alphen (dHvA) effect. Main dHvA branches are very similar to those of the 4 f -itinerant heavy fermion superconductor CeCoIn 5 , but the cyclotron effective masses are by one to two orders of magnitude smaller than those of CeCoIn 5 . These Fermi surface properties are well explained by the FLAPW energy band calculations.

De Haas-van Alphen effect and the electronic state in CePtAl

We have done the de Haas-van Alphen (dHvA) experiment for a canted ferromagnet CePtAl. The detected dHvA branches are so many in number, revealing the multiply connected small Fermi surfaces. The cyclotron effective masses are relatively large, ranging from 0.4 m 0 to 10 m 0 . These Fermi surfaces are approximately explained on the basis of the results of energy band calculations of LaPtAl.

Magnetic properties and Fermi surfaces in [formula omitted

We grew high-quality single crystals of NpIn 3 by the Indium-flux method and measured the magnetization and de Haas-van Alphen (dHvA) effect. The ferromagnetic and antiferromagnetic transitions were observed at T C = 14 K and T N = 10 K , respectively. The dHvA oscillations were detected at high fields, where the ferromagnetic state is realized. Three fundamental dHvA branches were clearly observed, which were discussed on the basis of the 5f-localized model.

Magnetic and Fermi Surface Properties in NpIn3

We succeeded in growing a high-quality single crystal of NpIn 3 by the In-flux method, and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas–van Alphen (dHvA) effect. Ferromagnetic and antiferromagnetic orderings occur at T C =14 K and T N =10 K, respectively, together with another transition at T * =8 K. When the magnetic field is applied to the sample, the antiferromagnetic state is finally changed into a ferromagnetic state with two metamagnetic transitions. The antiferromagnetic ordering and two metamagnetic transitions are found to be of the first-order phase transition. In the dHvA experiments, we observed three dHvA branches with the cyclotron mass ranging from 3.4 to 14 m 0 . These dHvA branches are discussed from a viewpoint of the 5 f -localized model based on the Fermi surface of LaIn 3 .

Electronic States in a Semimetal Ce3Sn7

We carried out the de Haas–van Alphen (dHvA) measurement and the pressure experiment of the electrical resistivity for an antiferromagnet Ce 3 Sn 7 with the orthorhombic crystal structure. The detected dHvA branches are many in number and their dHvA frequencies are extremely small in magnitude, indicating that Ce 3 Sn 7 is a semimetal. This is consistent with the result of the energy band calculations under the assumption that the 4 f electrons of two Ce atoms in the 2( a ) site are localized and the 4 f electron of one Ce atom in the 4( i ) site is itinerant. In the pressure experiment, the Neel temperature of T N = 5.3 K is found to slightly increase with increasing pressure, becomes maximum around 1 GPa, then decreases steeply with further increasing pressure and most likely becomes zero between 3 and 4 GPa. The antiferromagnetic state is changed into the non-magnetic state under pressure.

Single crystal growth and observation of the de Haas–van Alphen effect in ThIn 3

We have succeeded in growing a high-quality single crystal of ThIn 3 with the cubic structure by the In-flux method and measured the de Haas–van Alphen (dHvA) effect. Several dHvA branches were observed, ranging from 9.0 × 10 6 to 9.37 × 10 8 Oe . The experimental results are compared to the dHvA results of CeIn 3 under pressure of 2.7 GPa, together with the results of energy band calculations.

A change of the Fermi surface in CeRhIn 5 under pressure

We carried out the de Haas–van Alphen (dHvA) experiment for an antiferromagnet CeRhIn 5 under high pressures up to 3 GPa. The main dHvA branches α i and β 2 at ambient pressure, which are well explained by Fermi surfaces of LaRhIn 5, are unchanged up to about 2.4 GPa. Above 2.4 GPa, new dHvA branches appear, which are in good agreement with the corresponding dHvA branches of a 4f-itinerant heavy fermion superconductor CeCoIn 5. These results indicate that the 4f-electronic state is changed from localized to itinerant at a critical pressure P c ≃ 2.4 GPa .

Fermi surface ofLaRu4P12: A clue to the origin of the metal-insulator transition inPrRu4P12

We report the de Haas-van Alphen (dHvA) effect and magnetoresistance in the filled-skutterudite superconductor LaRu4P12, which is a reference material of PrRu4P12 that exhibits a metal-insulator (M-I) transition at T_MI~60 K. The observed dHvA branches for the main Fermi surface (FS) are well explained by the band-structure calculation, using the full potential linearized augmented-plane-wave method with the local-density approximation, suggesting a nesting instability with q =(1,0,0) in the main multiply connected FS as expected also in PrRu4P12. Observed cyclotron effective masses of (2.6-11.8)m_0, which are roughly twice the calculated masses, indicate the large mass enhancement even in the La-skutterudites. Comparing the FS between LaRu4P12 and PrRu4P12, an essential role of c-f hybridization cooperating with the FS nesting in driving the the M-I transition in PrRu4P12 has been clarified.

A Drastic Change of the Fermi Surface at a Critical Pressure in CeRhIn5: dHvA Study under Pressure

We carried out the de Haas–van Alphen (dHvA) experiment for an antiferromagnet CeRhIn 5 at high pressures up to 3 GPa. The cross-sectional areas of the Fermi surfaces due to main dHvA branches α i and β 2 at ambient pressure, which are well explained by two kinds of nearly cylindrical Fermi surfaces of a non-4 f reference compound LaRhIn 5 , are unchanged up to about 2.3 GPa, while the corresponding cyclotron masses m c * increase steeply above a pressure P * = 1.6 GPa where pressure-induced superconductivity sets in : m * c = 5.5 m 0 at ambient pressure, 20 m 0 at 1.6 GPa and 60 m 0 at 2.2 GPa for branch β 2 , for example. Above 2.4 GPa, new dHvA branches appear, which are in good agreement with the corresponding dHvA branches of a 4 f -itinerant heavy fermion superconductor CeCoIn 5 , indicating that the 4 f electron of CeRhIn 5 becomes itinerant and significantly contributes to the volume of the Fermi surface. The 4 f -electron character is thus changed from localized to itinerant at a critical pressur...

De Haas–van Alphen effect in [formula omitted] under pressure

We have carried out the de Haas–van Alphen (dHvA) experiment of an antiferromagnet CeRhIn 5 under pressure. The detected dHvA branches α i ( i = 1 , 2 , 3 ) and β 2 at ambient pressure are well explained by the corresponding dHvA branches in LaRhIn 5 , indicating that the f electron is localized at ambient pressure. At 2.9 GPa, where the antiferromagnetic ordering disappears completely, a new branch α i ( i = 1 , 2 , 3 ) appears. This is approximately the same as that of 4f-itinerant Fermi surface in CeCoIn 5 , suggesting that the 4f electronic state is changed into an itinerant one.

Electronic, Magnetic and Superconducting Properties of Quasi-two Dimensional Compounds Ce2RhIn8and La2RhIn8

We have measured the electrical resistivity, magnetic susceptibility, high-field magnetization, specific heat and de Haas–van Alphen (dHvA) oscillation of Ce 2 RhIn 8 , together with the dHvA oscillation of La 2 RhIn 8 . In La 2 RhIn 8 we detected three kinds of dHvA branches showing cylindrical Fermi surfaces, which are well explained by the result of FLAPW energy band calculations. The corresponding two dHvA branches were detected in Ce 2 RhIn 8 , indicating that the topology of the Fermi surface in Ce 2 RhIn 8 is approximately the same as that of La 2 RhIn 8 . The magnetic susceptibility and magnetization of Ce 2 RhIn 8 were analyzed on the basis of the crystalline electric field scheme of localized-4 f energy levels. Pressure-induced superconductivity was confirmed above 1.2 GPa from the resistivity and ac-susceptibility measurements.

An unusual hollow cylindrical Fermi surface of a quasi-two-dimensional compound CeAgSb2

Abstract We have carried out the de Haas-van Alphen (dHvA) experiment, together with electrical resistivity, magnetic susceptibility, magnetization and specific heat experiments on a high-quality single-crystal CeAgSb2, which has a small net ferromagnetic moment of 0.4 μB per Ce atom. The bulk magnetic properties are well explained by the crystalline electric field scheme. On the other hand, large dHvA frequencies of 108 Oe, which correspond to cylindrical Fermi surfaces, were detected by the dHvA measurement for the magnetic field along the tetragonal [001] direction, indicating the quasi-two-dimensional electronic structure. The dHvA branches of CeAgSb2 are highly different from those with small dHvA frequencies of 107 Oe for the reference compounds LaAgSb2 and YAgSb2 which exhibit a semimetallic character. The dHvA results have been compared with the results of the energy band calculations. It was concluded that the 4f electron is mainly localized and that the Fermi surface of CeAgSb2 is similar to tha...

Magnetic and Fermi Surface Properties of UCoGa5 and URhGa5

We succeeded in growing high-quality single crystals of UCoGa5 and URhGa5 by the self-flux method and measured the electrical resistivity, magnetic susceptibility, and de Hass-van Alphen(dHvA) oscillation. Three kinds of dHvA branches were observed, ranging from 8.6x 105 to 8.1 x 106Oe, which correspond to closed Fermi surfaces. UCoGa5 and URhGas are concluded to be semimetals. The cyclotron mass is small, ranging from 0.6 m0 to 2.9 m0.

Fermi Surface in CeRh2Si2under Pressure

We observed the de Haas–van Alphen (dHvA) oscillations in CeRh 2 Si 2 under pressures up to 1.54 GPa. Three dHvA branches at higher pressure than the critical pressure p c ≃1.06 GPa are well explained by the result of the 4 f -itinerant model. Their cyclotron masses are large, being 24 m 0 , 30 m 0 and 31 m 0 , which are about 4 times larger than the corresponding band masses.

De Haas–van Alphen Effect in UPd3

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.

De Haas-van Alphen effect in CeRh2Si2 under pressure

We observed de Haas-van Alphen (dHvA) oscillations in CeRh2Si2 at 1.3GPa, higher than the quantum critical pressure pc≃1.0GPa. 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.