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The results of X-ray diffraction, magnetic, and 155 Gd Mossbauer spectroscopy study, complemented by the a b - i n i t i o electronic structure and the hyperfine-interaction parameters calculations, of the GdRhO 3 orthorhodite are reported. GdRhO 3 crystallizes in the orthorhombic space group P n m a with the lattice parameters a = 5.7450 ( 1 ) A, b = 7.6647 ( 1 ) A, and c = 5.2905 ( 1 ) A. The evidence is provided for the presence of directional covalent bonding between the Rh and O atoms and of ionic bonding between the Gd and Rh/O atoms. GdRhO 3 orders antiferromagnetically with the Neel temperature T N = 2.13 ( 5 ) K. The magnetic susceptibility above T N follows the modified Curie-Weiss law with the paramagnetic Curie temperature of − 3.37 ( 1 ) K and the effective magnetic moment of 7.99(1) μ B per Gd atom. The Debye temperature of GdRhO 3 determined from the Mossbauer data is found to be 256(1) K. The calculated Gd magnetic moment and hyperfine-interaction parameters are in good agreement with the experimental values.

Crystals of ternary LnRu2P2 (Ln = Pr, Nd, Sm, Tb, Dy, Er) systems were synthesized, and their crystallographic, magnetic, and electric properties were investigated. All the crystals have a tetragonal ThCr2Si2-type structure of space group I4/mmm. The lattice constants decrease as the number of 4f electrons increases, reflecting the lanthanide contraction. An antiferromagnetic transition was observed for LnRu2P2 (Ln = Pr, Nd, Sm, Tb, Dy) at 25 K (Pr), 19 K (Nd), 15 K (Sm), 22.5 K (Tb), and 13 K (Dy). However, no transition was observed for ErRu2P2 down to 5 K. The Peff agrees well with the theoretical moment g J ( J + 1 ) of lanthanides, suggesting that lanthanides make a major contribution to the magnetic moment of LnRu2P2. A spin-flop-like transition was observed in the M(H) curves of PrRu2P2 and TbRu2P2 at 4 and 8 kOe, respectively; however, no saturation was observed up to 55 kOe.

Synthesis and characterization of Sr1−xAxPd3O4 (A = Na, Bi) are reported. All the doped phases crystallize in the cubic symmetry with the space group Pm3m. Both Hall and thermopower measurement results indicate that substitutions of Na+ and Bi3+ into the Sr2+ site introduce hole and electron carriers, respectively. As the dopant concentration increases, effective magnetic moment, electrical conductivity and carrier concentration of these phases increase and thermopower decreases. The highest power factor obtained among these doped samples is 0.5 μW/K2 cm at room temperature for Sr0.8Na0.2Pd3O4.

A series of orthorhombic NaLnTiO 4 (Ln = lanthanides) has been synthesized and characterized. These compounds all crystallize in A-site ordered n = 1 Ruddlesden–Popper phase (A n +1 B n O 3 n +1 ) structure. The weak ferromagnetism with large magnetization has been observed for Ln = Tb and Dy, and non-linear field dependence of magnetization without hysteresis has been observed for Ln = Er and Ho. By performing the symmetry operations, two possible canted spin arrangements have been proposed.

Ln 2 BaPdO 5 (Ln = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho) all crystallizes in Nd 2 BaZnO 5 structure which is proposed to have a Shastry–Sutherland (S–S) lattice of Ln 3+ ions. Ln 2 BaPdO 5 (Ln = Nd, Sm, Gd, Dy, Ho) exhibits antiferromagnetic transitions at temperatures between 2 and 5 K. In addition, metamagnetic transitions have been observed for Ln 2 BaPdO 5 (Ln = Nd, Dy, Ho) below 2 K. Specific heat of Ln 2 BaPdO 5 (Ln = Ho, Dy) exhibits symmetric peaks at T N , and residual entropy below T N is negligibly small. On the contrary, specific heat of Ln 2 BaPdO 5 (Ln = Nd, Sm, Gd) exhibits Schottky type anomalies followed by sharp peaks at T N , and residual entropy below T N is large. From these results, the applicability of the S–S model to Ln 2 BaPdO 5 with various Ln 3+ ions is proposed.

Single-phase polycrystalline samples of PbPdO 2 have been synthesized via solid-state reaction, and their electrical, magnetic and thermoelectric properties have been characterized. The temperature-dependent dc electrical resistivity exhibits metal–insulator transition around 90 K. Thermoelectric power and Hall effect measurement results indicate that the majority of carriers in PbPdO 2 are holes. The thermoelectric power is 95 μV/K at 290 K and large for metallic materials. Based on the temperature proportionality of thermoelectric power, PbPdO 2 is essentially a metal. The insulating behavior at low temperatures is driven by localization of charge carriers manifested by Curie paramagnetism.

The present study focuses on the crystallographic, electric, and magnetic properties of the new intermetallic compounds of NbPtSi and MRhSi (M=Nb, Ta) and the substitution effect on the superconductivity of TaPtSi in the system of Ta 1− x Nb x PtSi (0≤ x ≤1). The crystal structure of NbPtSi and MRhSi was refined assuming an orthorhombic Co 2 Si structure of the space group Pnma . MRhSi (M=Nb, Ta) has metallic conductivity and shows diamagnetic behavior at temperatures between 1.7 and 350 K. On the other hand, NbPtSi shows paramagnetic behavior with metallic conduction. In the Ta 1− x Nb x PtSi system, the superconductivity of TaPtSi ( T c =3.5 K) is suppressed by Nb substitution. The Nb-content dependence of the Pauli-paramagnetic susceptibility suggests that reduction of the density of states at the Fermi-level is a possible reason for the suppression of superconductivity.

The crystallographic, electric, and magnetic properties of the new intermetallic compounds HfMSi (M=Pt or Pd) and the superconductivity of HfRh 1− x Pd x Si were studied. The crystal structure of HfPtSi and HfPdSi could be refined assuming an orthorhombic structure (space group Pnma ) and lattice constants of a =0.6549 nm, b =0.3883 nm, and c =0.7506 nm for HfPtSi and a =0.6570 nm, b =0.3874 nm, and c =0.7565 nm for HfPdSi. Both compounds are metallic and show diamagnetic behavior below 300 K. A small effective electron mass is thought to be a reason for the diamagnetism of HfMSi (M=Pt or Pd). In the HfRh 1− x Pd x Si system, the superconductivity of HfRhSi ( T c =2.2 K) is suppressed by replacing Rh by Pd. The Pd content dependence of the Pauli paramagnetic susceptibility suggests that reduction of the density of states at the Fermi level is a possible cause of the suppression of superconductivity in the HfRh 1− x Pd x Si system.

The magnetism and transport properties of Hf 1− x Ta x Fe 2 (0.1≤ x ≤0.2) and Mn 2− x Cr x Sb ( x =0.1) were studied. Hf 1− x Ta x Fe 2 ( x >0.15) has a successive magnetic transition from ferromagnetism to paramagnetism via antiferromagnetism at temperatures between 150 and 350 K, and the transition has a considerable effect on the transport property. In particular, a specimen with x =0.155 shows a metamagnetic transition near room temperature, and a significant magnetoresistance as large as 12% is observed in accordance with the metamagnetic transition. Mn 1.9 Cr 0.1 Sb, which has a first-order magnetic transition from antiferromagnetism to ferrimagnetism at about 300 K, also shows a field-induced magnetic transition at 300 K, and the transition strongly affects the transport property. A giant magnetoresistance as large as 30% was observed at about 300 K under an applied field of 20 kOe. The metamagnetic transition seems to give rise to giant magnetoresistance via s–d scattering.

Crystallographic, magnetic and electric properties of metamagnetic Mn1−xCrxAu2 were studied. Pure MnAu2 has a helical-spin structure and the structure changes to a ferromagnetic state below the Neel temperature TN (∼360 K) and above a threshold magnetic field Hth (∼10 kOe at 300 K). The TN, Hth for the metamagnetic transition, and the helical angle of the helical-spin configuration decreases as the Cr content x increases. The Cr substitution seems to dilute the magnetism of MnAu2 and to weaken the interlayer magnetic coupling between the Mn spins. A significant magnetoresistance as large as 3.5% was observed at room temperature in magnetic fields below 10 kOe. The metamagnetic transition seems to give rise to the magnetoresistance via s–d scattering.

New intermetallic compounds, Hf3Ni4Ge4 and HfPtGe, were found and their crystallographic, electric and magnetic properties were characterized. Hf3Ni4Ge4 has an orthorhombic structure (space group Immm) with lattice constants of a=1.2873 nm, b=0.6484 nm, and c=0.3892 nm and shows typical Curie-paramagnetic behavior between 2 K and 300 K and a metallic temperature dependence of the resistivity at temperatures between 10 and 250 K. HfPtGe has an orthorhombic structure (space group Pnma) with lattice constants of a=0.6603 nm, b=0.3950 nm, and c=0.7617 nm and shows diamagnetism and a metallic temperature dependence of the resistivity.

The magnetic properties of CaRuO 3 were studied using polycrystalline and single-crystal samples. The M ( T ) curves of the polycrystalline sample showed irreversible behavior, and the M ( H ) curve showed weak ferromagnetic behavior below 60 K. No irreversible behavior was observed in the M ( T ) curves of a pseudo-cubic crystal sample at temperatures between 1.7 and 300 K. It was concluded that the irreversible behavior observed for the polycrystalline sample is not an intrinsic property of CaRuO 3 . The M ( H ) curve of the crystal sample showed peculiar behavior at 1.7 and 5 K, suggesting the existence of magnetic order at very low temperature. The Mossbauer study for the CaRu 0.99 57 Fe 0.01 O 3 crystal revealed that no magnetic order exists at temperatures down to 15 K; however, a sextet was observed at 2 and 5 K, suggesting the existence of magnetic order. Therefore, it was concluded from the results of magnetization and the Mossbauer measurements that no magnetic order exists at temperatures down to 15 K; however, possible magnetic order occurs in CaRuO 3 at a temperature below 15 K.

New superconducting intermetallic compounds with a chemical formula of MRhGe 2 (M=Zr, Hf) were discovered, and their crystallographic, magnetic, and electric properties were investigated. MRhGe 2 crystallizes in an orthorhombic TiMnSi 2 structure of space group Pbam and shows a superconducting transition at about 3 K. The magnetic susceptibility measurement indicated bulk superconductivity of MRhGe 2 . The superconducting parameters of MRhGe 2 (M=Zr, Hf) indicate that they are type-II superconductors in the category of the BCS theory.

Magnetic properties of Fe-Be compounds were studied. The highest value of both magnetization and Curie temperature was observed at the composition of FeBe2. Intensity of magnetization of these compounds suggests that each of Fe atom has different magnetic moment, which depends on the condition of their nearest neighbour atoms. Coercive force of I kOe and magnetization 4πMs of 7 kG/cm3 were obtained for a powder sample of FeBe2 with mean diameter of 1 μm.

Optimum composition was determined presisely on new oxide superconductor Bi-Sr-Cu-O system and substitution effects on Bi-Sr-Cu-O and Bi-Sr-Ca-Cu-O system were studied by electric and magnetic measurements. Maximum Tc (onset 10K) was observed at the composition ratio of Bi:Sr:Cu=1:1:1 (designated as BiSrCuOy) in the Bi2O3-SrCO3-CuO ternary system. Transition temperatures were increased with the substitution of light rare earth elements or Ca for Bi or Sr but were decreased with any other substitution. In the case of Bi-Sr-Ca-Cu-O system substitution with Pb, La, Nd, Yb or Lu for Bi or Sr are considered to be valuable for improvement of Tc and for obtaining single phase superconductor.