Toshikazu Uchida

Magnetic properties of RRhO3 (R=rare earth)

Abstract RRhO 3 (R=rare earth except Ce and Pm) was prepared by a solid-state reaction, and its crystallographic, magnetic, and electric properties were investigated. RRhO 3 has an orthorhombic perovskite-type structure of the space group Pbnm . RRhO 3 shows Curie–Weiss paramagnetism above 5 K. On the other hand, EuRhO 3 shows antiferromagnetic behavior. The Rh 3+ ion, which seems to be in the low-spin state, has a very small effective magnetic moment ( P eff =0.295 μ B /ion). The P eff value of the RRhO 3 compounds shows the same dependence on the number of 4 f electrons as the gJ value of the rare-earth ions. The rare-earth ions make a major contribution to the magnetic moment of RRhO 3 . The resistivity of all RRhO 3 shows an activation-type (or semiconductor-like) temperature dependence.

New intermetallic compounds found in Hf–Ni–Ge and Hf–Pt–Ge systems

Abstract 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.

Magnetic properties of Sm6Fe23 crystal

A single crystal of Sm6Fe23 was prepared by means of a modified self-flux method, and its crystallographic magnetic properties were studied. Sm6Fe23 has the cubic Th6Mn23-type structure (space group Fm3m) with a lattice constant of a=1.2187±0.0006 nm. The easy axis of magnetization is parallel to the 〈111〉 direction. Its magnetic moment per unit formula deduced from the saturation magnetization is 59 μB at 5 K, a value that is consistent with the value calculated assuming ferromagnetic coupling between the Sm and Fe sublattices. The cubic anisotropy constants K1 and K2 estimated from the magnetization curves of the [111], [110], and [100] directions are −2.7×106 and 6.3×105 erg/cm3, respectively. The anisotropy field HA calculated from the anisotropy constants is 6.1 kOe.

Synthesis and properties of Ba3NaRu2O9-δ and Ba3(Na, R)Ru2O9-δ (R=rare earth) crystals

Abstract Crystals of Ba3NaRu2O9−δ (δ≈0.5) and Ba3(Na, R)Ru2O9−δ (R=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) were grown by an electrochemical method, and their crystallographic, magnetic, and electric properties were studied. All crystals have a hexagonal structure of space group P63mmc. Ba3NaRu2O9−δ and Ba3(Na, R)Ru2O9−δ (except Ce) have a negative asymptotic Curie temperature suggesting the existence of an antiferromagnetic order; however, they are paramagnetic at temperatures above 1.7 K. Ba3NaRu2O9−δ has an effective magnetic moment Peff of 0.91 μB, while Peff of Ba3(Na, R)Ru2O9−δ (except Ce) reflects the large free-ion moment g J(J+1) of the rare earth ions. Ba3(Na, Ce)Ru2O9−δ shows peculiar magnetic behavior that differs from the magnetism of other Ba3(Na, R)Ru2O9−δ crystals. The resistivity of all crystals exhibits an activation-type temperature dependence with an activation energy in the range of 0.1∼0.2 eV.

Magnetic properties of Sm(Fe1−xAlx)7 crystals

Abstract Sm(Fe 1− x Al x ) 7 ( x =0, 0.047, 0.07 and 0.12) crystals were grown by the self-flux method, and their crystallographic and magnetic properties were investigated. Sm(Fe 1− x Al x ) 7 crystallizes in a tetragonal structure of the space group P4 2 /mnm , and aluminum occupies the iron site. The structure is very similar to that of Nd 2 Fe 14 B except that the boron sites are vacant. The Curie temperature, T C , increases with a modest Al substitution in spite of little changes in the saturation magnetization M s . However, both T C and M s decrease for a higher Al substitution. All the specimens have negative K 1 and positive K 2 . The easy axis of magnetization is parallel to the [100] direction since K 1 +2 K 2 K 1 +2 K 2 decreases and becomes closer to zero with increasing Al content, aluminum substitution seems to be ineffective to change the easy direction from the basal plane to the c -axis.