Tetsuo Shimura

Novel two-dimensional conductor Sr2RhO4

Abstract A new complex oxide Sr 2 RhO 4 with K 2 NiF 4 -type structure has been synthesized. The crystal symmetry of Sr 2 RhO 4 is orthorhombic, and the temperature coefficient of resistivity is positive down to 10 K. Magnetic susceptibility measurement revealed a two-dimensional nature of the magnetic ordering.

Control of ferromagnetic transition temperature of LaxMnyO3 by lithium insertion

Abstract Lithium was electrochemically inserted into perovskite-type oxide La x Mn y O 3 with both rhombohedral and orthorhombic symmetries. Ferromagnetic transition temperature( T c ) of lithiated rhombohedral Li z La x Mn y O 3 first decreased then increased with an increase in z . This result was clearly explained by the change in the structure with the insertion.

Candidate compounds for superconductivity

Non-cupreous compounds with perovskite-related structures containing V 4+ (3d 1 ), Co 3+ (3d 6 ), and Rh 3+ (4d 6 ) were synthesized and their properties were investigated. A metallic d 1 compound Sr 4 V 3 O 10-δ with the layered structure showed a semiconducting resistivity at low temperatures by an increase of the oxygen vacancies or by a substitution of V by Ti. Semiconducting perovskite-related compound LaRhO 3 with the low spin configuration of Rh 3+ (4d 6 ) could be hole-doped in the d e orbitals by the substitution of La by Sr or Ca, and showed a metallic conductivity, while LaSrRhO 4 with the K 2 NiF 4 structure and the low spin configuration could not be hole-doped by decreasing the La/Sr ratio.

Preparation and Properties of Sr2-xLaxRhO4 and Sr2-xAxIrO4 (A = Ca and Ba)

K2NiF4 type structure solid solution systems Sr2-x La x RhO4 (0≤x≤1) and Sr2-x A x IrO4 (A = Ca and Ba) were prepared and those electrical and magnetic properties were investigated. Sr2RhO4 exhibits metal-like temperature dependence of resistivity and antiferromagnetic ordering of Rh4+, but when x increases more than 0.3 both phenomena disappears. Sr2IrO4 shows spontaneous magnetization below 230 K, and this transition temperature is not influenced by a small change of lattice parameter with Ca or Ba substitution.