22 research outputs found
From Mott insulator to ferromagnetic metal: a pressure study of CaRuO
We show that the pressure-temperature phase diagram of the Mott insulator
CaRuO features a metal-insulator transition at 0.5GPa: at 300K from
paramagnetic insulator to paramagnetic quasi-two-dimensional metal; at
12K from antiferromagnetic insulator to ferromagnetic, highly anisotropic,
three-dimensional metal. % We compare the metallic state to that of the
structurally related p-wave superconductor SrRuO, and discuss the
importance of structural distortions, which are expected to couple strongly to
pressure.Comment: 4 pages, 4figure
Anisotropic Release of the Residual Zero-point Entropy in the Spin Ice Compound Dy2Ti2O7: Kagome-ice Behavior
We report the specific heat and entropy of single crystals of the spin ice
compound Dy2Ti2O7 at temperatures down to 0.35 K. We apply magnetic fields
along the four characteristic directions: [100], [110], [111] and [112].
Because of Ising anisotropy, we observe anisotropic release of the residual
zero-point entropy, attributable to the difference in frustration
dimensionality. In the high magnetic field along these four directions, the
residual entropy is almost fully released and the activation entropy reaches
Rln2. However, in the intermediate field region, the entropy in fields along
the [111] direction is different from those for the other three field
directions. For the [111] direction the frustration structure changes from that
of three-dimensional(3D) pyrochlore to that of two-dimensional(2D) Kagome-like
lattice with constraint due to the ice rule, leading to different values of
zero-point entropy.Comment: 4 pages, 4 figures, to appear in Phys. Rev.
Cyclotron resonance and mass enhancement by electron correlation in KFeAs
Cyclotron resonance (CR) measurements for the Fe-based superconductor
KFeAs are performed. One signal for CR is observed, and is attributed
to the two-dimensional Fermi surface at the point. We found a
large discrepancy in the effective masses of CR [(3.40.05) ( is
the free electron mass)] and de-Haas van Alphen (dHvA) results, a direct
evidence of mass enhancement due to electronic correlation. A comparison of the
CR and dHvA results shows that both intra- and interband electronic
correlations contribute to the mass enhancement in KFeAs.Comment: 5 pages, 4 figure
S = 1 2 パイロクロア サンカブツ ノ ジキテキ キテイ ジョウタイ
京都大学0048新制・課程博士博士(理学)甲第9921号理博第2582号新制||理||1321(附属図書館)UT51-2003-H342京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 前野 悦輝, 教授 山田 耕作, 教授 藪崎 努学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA