Tetuo Ohoyama

Magnetic Properties of Intermetallic Compounds in Iron-Germanium System : Fe1.67Ge and FeGe2

The magnetic properties of the two intermetallic compound β phase (Fe 1.67 Ge) and δ phase (FeGe 2 ), in Fe-Ge system, were investigated. The β phase has B8 2 type of crystal structure and is ferromagnetic with the Curie point 485°K, saturation magnetization at 0°K 1.59 µ B , and paramagnetic moment 3.14 µ B per iron atom. The δ phase has C16 type of crystal structure and exhibits a parasitic ferromagnetic behavior in which the Neel point, asymptotic Curie point, saturation magnetization at 0°K, and paramagnetic moment are 190°K, +90°K, 0.11 µ B , and 2.43 µ B , per iron atom respectively. Brief discussions on the magnetic structures were given.

X-ray and Magnetic Studies of the Manganese-Germanium System

The constitution of Mn–Ge system within the range of composition 21.8∼35.7 at.% Ge was examined X-ray powder diffraction, and magnetic properties of each phase were studied. The existence of four phases–high- and low-temperature phases at about 22∼23.5 at.% Ge ( e , e 1 ), a high temperature phase around 28 at.% Ge (ζ) and a low-temperature phase at 28.6 at.% Ge (κ)–was established. The κ phase is ferrimagnetic below the Curie point 710°K, and the spontaneous magnetization is reversed at 395°K (N type). The other phases exhibit quite anomalous magnetism. The Debye diagram for ζ phase could be indexed assuming a hexagonal structure with lattice parameters a =7.18 6 A and c =13.0 8 A.

Magnetic and X-Ray Studies of Iron-Germanium System II. Phase Diagram and Magnetism of Each Phase

Constitution of iron-germanium system is discussed based on x-ray and magnetic studies, and a new phase diagram is proposed. Fe solid solution (α) ranges up to 20.4 at.% Ge at 710°C and to 21.3 at.% Ge at 520°C. Homogeneity range of the most iron rich compound ( e above 700°C and e 1 below) are 23.8–26 at.% Ge at 710°C ( e ) and 24.2–25.8 at.% Ge at 580°C ( e 1 ). At 50 at.% Ge, ξ phase has a narrow range below 700°C. In α (b. c. c.) solid solution of iron, the saturation magnetization and Curie point decrease to 150 emu/g and 885°K respectively. Crystal structures of e and e 1 phases are Ni 3 Sn(D0 19 ) and Cu 3 Au(L1 2 ) type, and the saturation magnetization of both phases is about 150 emu/g, while the Curie points are 650°K for e and 760°K for e 1 . ζ Phase has CoSn (B35) type of structure and is paramagnetic, the moment being 2.8µ B /Fe. Magnetic interaction and magnetic structures are also discussed.

Magnetic Property of (Co, Ni)1.67Ge

The susceptibilities of Co 1.67 Ge and Ni 1.67 Ge are nearly independent of temperature, and the values are 4.9×10 -6 and 0.4×10 -6 emu/g respectively. From the magnetic measurement on a series of alloys of (Co, Ni) 1.67 Ge, it is concluded that these alloys are of Pauli paramagnetism. The density of states is calculated as a function of energy, and then the effective mass ratio is estimated on the basis of the free electron theory. The ratio m * / m is about 28 for cobalt rich side, and 5 for nickel rich side. Therefore the magnetism of Co 1.67 Ge and Ni 1.67 Ge may be ascribed to the Pauli paramagnetism of 3 d holes and 4 s electrons respectively. These conclusion is consistent with a theory previously proposed.