Kindo Koichi

Magnetic Properties of Single Crystalline RCu2Si2 (R: Rare Earth)

A series of ternary compounds RCu 2 Si 2 (R: rare earth) has been grown in single-crystalline form by the flux method. The magnetic properties of these compounds were investigated by measuring the lattice parameter, electrical resistivity, magnetic susceptibility, and magnetization. All the compounds crystallize in the tetragonal ThCr 2 Si 2 -type structure. Most of these compounds order antiferromagnetically at low temperatures, except when R=Y, La, Yb, and Lu. The magnetic anisotropy in the susceptibility and magnetization at low temperatures is found to be relatively small despite the tetragonal crystal structure. An increase in the electrical resistivity just below the ordering temperature and a first-order-like transition are characteristic features of RCu 2 Si 2 with R = light rare earth and R = heavy rare earth, respectively.

Quantum Magnetization Plateau in Spin-1 Triangular-Lattice Antiferromagnet Ba3NiSb2O9

We report the results of magnetization and specific heat measurements on Ba 3 NiSb 2 O 9 , which is a quasi-two-dimensional spin-1 triangular-lattice antiferromagnet. We observed a nonclassical magnetization plateau at one-third of the saturation magnetization that is driven by spin frustration and quantum fluctuation. Exact diagonalization for a 21-site rhombic cluster was performed to analyze the magnetization process. Experimental and calculated results agree well.

Gapped Ground State in the Spin-\(\frac{{\bf 1}}{{\bf 2}}\) Trimer Chain System Cu 3Cl 6(H 2O) 2·2H 8C 4SO 2

The magnetic susceptibility and magnetization curves of an \(S=\frac{1}{2}\) trimer spin chain system Cu 3 Cl 6 (H 2 O) 2 ·2H 8 C 4 SO 2 have been measured using single crystals and polycrystals. I...

Field-Induced Quadrupolar Ordered Phase for H∥ in Heavy-Fermion Compound YbCo2Zn20

Magnetic susceptibility, high-field magnetization up to 500 kOe, and specific heat in a wide temperature range from 0.06 to 300 K were measured for single crystals of the cubic heavy-fermion compound YbCo 2 Zn 20 in order to elucidate the electronic states of the compound at low temperatures. A strong increase in the magnetic specific heat in the form of C mag / T below ∼1 K is approximately explained by the resonant level model for S = 1/2 with the Kondo temperature T K = 1 K, and an extremely large C mag / T ≃8 J/(K 2 ·mol) below about 0.2 K is explained by considering the magnetic entropy of the doublet ground state in the 4 f crystalline electric field (CEF) scheme of an Yb 3+ ion, which corresponds to an extremely large electronic specific heat coefficient. The field-induced ordered phase for H ∥ , which has recently been found by low-temperature magnetization measurements, was precisely studied by electrical resistivity and specific heat measurements, and was observed in a limited angular range ...

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 .

Anisotropic Magnetic Properties of a Pressure-induced Superconductor Ce2Ni3Ge5

Single crystals of a pressure-induced superconductor Ce 2 Ni 3 Ge 5 have been successfully grown by the flux method. The anisotropic magnetic properties due to the orthorhombic crystal structure have been studied precisely by the electrical resistivity, specific heat, magnetic susceptibility, and high-field magnetization measurements. The results of these measurements confirmed two antiferromagnetic transitions at T N1 =5.0 K and T N2 =4.3 K. The electronic specific heat coefficient obtained from the low-temperature specific heat data amounts to 90 mJ/K 2 ·mol Ce. The high-field magnetization for H ∥[100] shows four magnetic transitions at 11.8, 12.9, 17.5 and 23.9 T with a saturation moment of 0.73 µ B /Ce at 1.3 K. On the other hand, two magnetic transitions are observed for H ∥[010] and [001], with saturation moments of 0.43 and 1.1 µ B /Ce, respectively. We have also performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and magnetization to understand the magnetocrysta...

High-field magnetization of USn3 and UPb3

UX 3 (X=Si, Ge, Sn and Pb) compounds with the cubic crystal structure are interesting in relation with the lattice constant and the electronic state of 5 f electrons.We measured the high-field magnetization of USn 3 and UPb 3 grown by the self-flux method.The broad metamagnetic transition was observed in a heavy fermion paramagnetic compound USn 3 at about 30 T, which is similar to the metamagnetism of UPt 3 . On the other hand, the sharp metamagnetic transitions were observed in an antiferromagnetic compound UPb 3 .

Almost Perfect Frustration in the Dimer Magnet Ba2CoSi2O6Cl2

We determined the crystal structure of Ba2CoSi2O6Cl2, which was synthesized in this work, and investigated its quantum magnetic properties using single crystals. This compound should be described as a two-dimensionally coupled spin-1/2 XY-like spin dimer system. Ba2CoSi2O6Cl2 exhibits a stepwise magnetization process with a plateau at half of the saturation magnetization, irrespective of the field direction, although all the Co2+ sites are equivalent. This indicates that spin triplets are localized owing to the almost perfect frustration of interdimer exchange interactions. Thus, the spin states for the zero and 1/2 magnetization-plateau states are almost exactly given by the simple product of singlet dimers and the alternate product of singlet and triplet dimers, respectively.

Magnetic and Fermi Surface Properties in PrRh3B2

We have grown a single crystal of PrRh 3 B 2 with the hexagonal structure and measured the electrical resistivity, specific heat, de Haas–van Alphen oscillation, magnetic susceptibility, high-field magnetization, thermal expansion and magnetostriction. PrRh 3 B 2 is not a simple ferromagnet as reported previously, but a ferrimagnet with an ordering temperature T ord =3.6 K. The Schottky specific heat observed around 25 K and the large anisotropy of the magnetic susceptibility and magnetization are found to be well explained by the crystalline electric field (CEF) with a large overall CEF-splitting energy of 1080 K and a strong ferromagnetic exchange interaction along the [0001] direction. The topology of the Fermi surface in PrRh 3 B 2 is similar to that of the non-4 f reference compound LaRh 3 B 2 , exhibiting a quasi-one-dimensional character of the electronic states.

Collapse of Magnetic Order of the Quasi One-Dimensional Ising-Like Antiferromagnet BaCo2V2O8 in Transverse Fields

We have performed magnetization measurements of the quasi one-dimensional (1D) \(S = 1/2\) Ising-like anti ferromagnet BaCo2V2O8 in transverse fields. Different from the expectation by the 1D \(S = 1/2\) \(XXZ\) model, a steep suppression of the antiferromagnetic order is observed for \(H\parallel[100]\), whereas the experimental results for \(H\parallel[110]\) agree with the \(XXZ\) model. We show that these anisotropic behaviors are caused by a characteristic screw chain structure in BaCo2V2O8, which gives rise to a peculiar angular dependence of effective fields upon application of uniform external magnetic fields.