Kida Takanori

Unusual Magnetic State with Dual Magnetic Excitations in the Single Crystal of S = 1/2 Kagome Lattice Antiferromagnet CaCu3(OH)6Cl2 ∙ 0.6H2O

We have succeeded in preparing single crystals of CaCu3(OH)6Cl2 ∙ 0.6H2O, a candidate for the S = 1/2 Kagome lattice antiferromagnet. Magnetic properties of the compound are dominated by the nearest neighbor antiferromagnetic interaction J1, and the next nearest neighbor ferromagnetic J2 and an antiferromagnetic Jd across a hexagon, which is different from related compounds Kapellasite and Haydeeite with ferromagnetic J1. Magnetic susceptibility exhibits a sudden increase below 13 K and a cusp anomaly at T* = 7.2 K in the ab-plane, whereas only a moderate enhancement is observed below T* along the c-axis. A tiny peak detected in heat capacity at T* indicates the occurrence of a magnetic phase transition. The low temperature magnetic heat capacity was reproduced by assuming a two-dimensional spin-wave component and a temperature-linear term. The spin-wave contribution suggests a magnon excitation in a short-range ordered region, whereas the relatively large T-linear term 5.9 mJ/(Cu-mol·K2) at H = 0 T of th...

Absence of Magnetic Long Range Order in Ba3ZnRu2O9: A Spin-Liquid Candidate in the S = 3/2 Dimer Lattice

We have discovered a novel candidate for a spin liquid state in a ruthenium oxide composed of dimers of S = 3/2 spins of Ru5+, Ba3ZnRu2O9. This compound lacks a long range order down to 37 mK, which is a temperature 5000-times lower than the magnetic interaction scale of around 200 K. Partial substitution for Zn can continuously vary the magnetic ground state from an antiferromagnetic order to a spin-gapped state through the liquid state. This indicates that the spin-liquid state emerges from a delicate balance of inter- and intra-dimer interactions, and the spin state of the dimer plays a vital role. This unique feature should realize a new type of quantum magnetism.We have discovered a novel candidate for a spin liquid state i n a ruthenium oxide composed of dimers of S = 3/2 spins of Ru, Ba3ZnRu2O9. This compound lacks a long range order down to 37 mK, which is a temperature 5000times lower than the magnetic interaction scale of around 20 0 K. Partial substitution for Zn can continuously vary the magnetic ground state from an antiferromagnetic order to a s pin-gapped state through the liquid state. This indicates that the spin-liquid state emerges from a delicate balance o f interand intra-dimer interactions, and the spin state of the dimer plays a vital role. This unique feature should realize a new type of quantum magnetism.

Magnetic-Field-Induced Metallic State in β-US2

β-US 2 with the orthorhombic structure is an interesting compound of which the electrical property is changed from a metallic state to an insulating state at temperatures lower than 80 K. To clarify the present metal–insulator change, we carried out the magnetization and magnetoresistance measurements in magnetic fields up to 50 T. The magentization at 4.2 K saturates above 40 T, reaching 1.75 µ B /U at 50 T for the magnetic field along the magentic easy-axis, namely the [001] direction. The corresponding electrical resistivity at 4.2 K is steeply reduced in magnitude from 1 ×10 3 Ω·cm to 2 ×10 -2 Ω·cm at 50 T only when the magnetic field is applied along the [001] direction. The temperature dependence of the electrical resistivity at 50 T indicates a usual metallic behaviour. The conduction electrons are most likely released from the trapped U-sites when the 5 f -CEF magnetic moments are fully polarized in high magnetic field of 50 T. The present experimental results are discussed from the viewpoint of t...

Magnetic-field-induced Quantum Phase in S = 1/2 Frustrated Trellis Lattice

We present a new model compound of an S = 1/2 frustrated system with ferromagnetic interaction composed of verdazyl radical β-2,3,5-Cl3-V. The ab initio molecular orbital calculation indicates the formation of an S = 1/2 trellis lattice in which zigzag chains and ladders with ferromagnetic rung interaction are two-dimensionally coupled. We observe a field-induced successive phase transition and an unconventional change in the magnetization curve near the saturation field, accompanied by T2 dependence on the magnetic specific heat. A two-dimensional spin-nematic state attributed to the ferromagnetic rung interactions is a possible candidate for the ground state in high-field regions.

Effects of Magnetic Field and Pressure on the Valence-Fluctuating Antiferromagnetic Compound EuPt2Si2

The effects of a magnetic field and pressure on the Kondo-like behavior in the valence-fluctuating antiferromagnetic compound EuPt2Si2 were studied using single-crystalline samples. The logarithmic...

Development of a Two-Axis Rotator in Pulsed High Magnetic Fields for a Magnetic Torque Measurement

We present a magnetic torquemeter utilizing a piezoresistive microcantilever for use in pulsed high magnetic fields. Pulsed high magnetic fields are generated with a non-destructive pulsed magnet, which has a large bore diameter (48 mm) and a large sample space size (33 mm). Since differential gears are built into the sample space of this apparatus, it is possible to change sample angles against the magnetic field direction freely. By using this apparatus, we have performed the de Haas–van Alphen (dHvA) measurement on a high-quality Pb single crystal.