Masayasu Ishikawa

Bulk ferromagnetism in the β-phase crystal of the p-nitrophenyl nitronyl nitroxide radical

Transition to a ferromagnetic long-range ordered state was found at 0.60 K in the orthorhombic β-phase crystal of p-nitrophenyl nitronyl nitroxide (or 2-(4′-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-N-oxide in the IUPAC nomenclature). This finding follows our recent discovery of the first organic bulk ferromagnet in the triclinic γ-phase crystal of the same compound.

Superconducting and Magnetic Properties of Filled Skutterudite Compounds RERu4Sb12(RE=La,Ce,Pr,Nd and Eu).

We have studied superconducting and magnetic properties of RERu 4 Sb 12 prepared by an Sb-flux method and found that LaRu 4 Sb 12 is superconducting below 3.58 K and PrRu 4 Sb 12 is a Van Vleck paramagnet which becomes superconducting below 1.04 K. CeRu 4 Sb 12 is a unique substance which shows intermediate-valence behavior with a characteristic broad peak around 100 K in the magnetic susceptibility and Kondo-like behavior in the electrical resistivity at high temperatures. Furthermore, non-Fermi liquid behavior is observed in the specific heat and electrical resistivity at low temperatures. NdRu 4 Sb 12 and EuRu 4 Sb 12 show a magnetic transition at 1.3 K and 3.3 K, respectively.

First observation of an antiferromagnetic phase in the Y1Ba2Cu3Ox system

The magnetic properties of four different phases of the YBa2Cu3Ox system, including the famous 90 K superconductor, have been probed by the positive muon spin relaxation method (µ+SR). The oxygen-deficient tetragonal insulating phase (x~6.2) was found to be magnetically ordered, thus most likely antiferromagnetic, near room temperature.

Gap Formation in a Valence Fluctuation System of CeNiSn

We have found that CeNiSn is a typical valence fluctuating compound with a pseudo gap near the Fermi level. The valence fluctuating state in CeNiSn is gradually converted to Kondo regime by a partial replacement of Ni by Cu.

Effects of oxygen stoichiometry and ordering in Ba2YCu3Oy (6≤y≤7)

Abstract We undertook a careful investigation on the effects of oxygen stoichiometry and ordering in BYCO samples prepared by an improved technique and found conspicuous effects of oxygen ordering in various properties. The present results of resistivity, magnetic susceptibility and specific heat experiments provide strong evidences for decisive role of the ordering of CuO chain around Cu(1) sites. From low temperature specific heat measurements, we found an almost constant residual λ ∗ value in the whole range of y, which is tentatively interpreted as due to low energy excitations of the spins of Cu(2).

Nuclear Spin-Lattice Relaxation of 63,65Cu at the Cu(2) Sites of the High Tc Superconductor YBa2Cu3O7-δ

Nuclear spin-lattice relaxation times T 1 of 63 Cu and 65 Cu in the Cu(2) sites of the high T c superconductor YBa 2 Cu 3 O 7-δ (δ≃0.1, T c =91 K) have been measured for the wide temperature range between 2.2 K and 300 K. The temperature dependence of 1/ T 1 in the normal state has been found to be the one unexpected for simple metals. The influences of antiferromagnetic spin fluctuations in the d–p bands in the Cu(2)–O layers are discussed. The temperature dependence of 1/ T 1 below T c has also been found to be the one which is not expected for isotropic BCS superconductors. The power-law like temperature dependence of 1/ T 1 without any enhancement just below T c has been observed between 40 K and 91 K.

Bandwidth control in a perovskite-type 3 d 1 -correlated metal Ca 1 − x Sr x VO 3 . I. Evolution of the electronic properties and effective mass

Single crystals of the perovskite-type

ANOMALOUS MAGNETIC PROPERTIES OF CERU4SB12

{3d}^{1}

An organic ferromagnet: α-phase crystal of 2-(2′,5′-dihydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy-3-oxide (α-HQNN)

metallic alloy system

Characterization of Metamorphic Phases of Ba2YCu3O9-δ

{\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{VO}}_{3}