A.V. Morozkin

Analysis of the melting temperatures of RT2 compounds (MgCu2 structure) (R=Rare Earth, TMn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) and RT2X2 compounds (RLa, Ce, Sm, Er; TMn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt; XSi, Ge)

Abstract Physico-chemical analysis techniques, including X-ray phase analysis and differential thermal analysis were employed for the characterisation of compounds including their melting temperature. The melting temperature for 70 RT 2 X 2 compounds has been measured (R=(La, Ce, Sm, Er, Tm), T=(Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt), X=(Si, Ge)). It is established, that the compounds CePt 2 Ge 2 , LaPt 2 Si 2 , LaPt 2 Ge 2 belong to the CaBe 2 Ge 2 structure type (group P4/mmm ): LaPt 2 Si 2 ( a =0.4280(2) nm, c =0.9831(6) nm); LaPt 2 Ge 2 ( a =0.4417(3) nm, c =0.976(2) nm) and CePt 2 Ge 2 ( a =0.44033(4) nm, c =0.9808(1)). An empirical model able to describe the melting temperature of T m of the compounds RT 2 , RT 2 X 2 with accuracy often better than 5% is presented: T m = const /V 1 3 , where the constant factor depends on the type of atoms constituting the compound, and where V is unit cell volume.

New Sc2Re3Si4-type R2Ti3Si4 compounds and their magnetic properties (R=Gd-Er)

Abstract Powder X-ray diffraction investigations and macroscopic magnetic properties of new ternary Sc 2 Re 3 Si 4 -type R 2 Ti 3 Si 4 compounds (R=Gd–Er) are reported. The compounds (Gd 0.95 ) 2 Ti 3 Si 4 ( a =0.6997(2) nm, c =1.2878(4) nm), Tb 2 Ti 3 Si 4 ( a =0.7006(1) nm, c =1.2875(2) nm), Dy 2 Ti 3 Si 4 ( a =0.6976(1) nm, c =1.2814(2) nm), Ho 2 Ti 3 Si 4 ( a =0.6970(1) nm, c =1.2793(2) nm) and Er 2 Ti 3 Si 4 ( a =0.6964(1) nm, c =1.2777(1) nm) crystallize in the tetragonal Sc 2 Re 3 Si 4 -type structure (space group P 4 1 2 1 2; No. 96). The Gd 2 Ti 3 Si 4 , Tb 2 Ti 3 Si 4 and Er 2 Ti 3 Si 4 compounds are Curie–Weiss paramagnets down to 4 K.

Crystallographic data of new ternary Sm5Ge4-type R2Ti3Ge4 compounds (R=Gd-Er)

Abstract Investigations made by powder X-ray diffraction on five new ternary R2Ti3Ge4 compounds (R=Gd-Er) are reported. The (Gd0.97)2Ti3Ge4 (a=0.7042(1) nm, b=1.3494(2) nm, c=0.7186(1) nm), (Tb0.99)2Ti3Ge4 (a=0.7019(1) nm, b=1.3457(2) nm, c=0.7156(1) nm), (Dy0.97)2Ti3Ge4 (a=0.6987(1) nm, b=1.3409(2) nm, c=0.7122(1) nm), (Ho0.96)2Ti3Ge4 (a=0.6981(1) nm, b=1.3399(2) nm, c=0.7117(1) nm) and (Er0.91)2Ti3Ge4 (a=0.6962(1) nm, b=1.3367(2) nm, c=0.7099(1) nm) crystallize in the orthorhombic Sm5Ge4-type structure (space group Pnma).

Magnetic properties of ternary scandium rare earth silicides and germanides

The magnetic, electric and crystallographic properties of RScSi and RScGe (R=Gd, Tb, Dy, Ho, Er and Y) compounds were studied. The existence of new ferromagnetic and antiferromagnetic compounds with high magnetic ordering temperatures has been established. The investigated compounds are characterized by low 3d-electron concentration and strong exchange interactions between rare earth ions via itinerant 3d- and 4p-electrons. The obtained results are compared with observations on similar RTiGe compounds.

CeScSi- and CeFeSi-type structures in compounds derived from GdTiGe

Abstract Physico-chemical analysis techniques, including X-ray phase analysis and metallographic analysis were employed in investigations of the solid solutions based on GdTiGe compounds. These solid solutions have existence regions of the CeScSi-type phase, the CeFeSi-type phase and of their mixture. Gd 0.9 TiGe, Sm x Gd 1− x TiGe ( x =0–0.1, 0.9–1), GdSc x Ti 1− x Ge ( x =0–0.1), Y x Gd 1− x TiGe ( x =0–1), Gd{Zr, Hf, V, Nb, Cr, Cu} 0.15 Ti 0.85 Ge, Gd{V, Mn} 0.3 Ti 0.7 Ge, GdTiGe 0.9 Si 0.1 form coherent mixtures of the CeScSi-type and CeFeSi-type phases, while GdTi 0.9 Ge and the solid solutions Sm x Gd 1− x TiGe ( x =0.2–0.9), GdSc x Ti 1− x Ge ( x =0.15–1), GdMo 0.15 Ti 0.85 Ge, Gd{Zr, Hf, Nb} 0.3 Ti 0.7 Ge, GdTiGe 0.9 {C, Sn, Pb} 0.1 form the CeScSi-type phase only. GdTiGe 0.9 forms in the CeFeSi-type structure. The replacement of Gd, Ti, Ge in GdTiGe by R-, T-, X-atoms, that facilitate the X–X interaction, leads to the formation of the CeScSi-type structure (R=rare earths, T=transition metals, X=p-elements). The magnetic ordering temperature of Sm x Gd 1− x TiGe compounds decreases with increasing Sm content: Sm 0.05 Gd 0.95 TiGe ( T m =365 K), Sm 0.3 Gd 0.7 TiGe ( T m =333 K), Sm 0.8 Gd 0.2 TiGe ( T m =297 K). GdSc 0.3 Ti 0.7 Ge ( T C =344 K), GdHf 0.3 Ti 0.7 Ge ( T C =398 K), GdV 0.3 Ti 0.7 Ge ( T C =370 K) and GdMn 0.3 Ti 0.7 Ge ( T C =376 K) give rise to a ferromagnetic type of ordering, while the GdNb 0.3 Ti 0.7 Ge ( T N >412 K) exhibits an antiferromagnetic type of ordering. The magnetic ordering temperature of these compounds increase with increasing c cell parameters.

Phase equilibria in the Sm{{Ru,Rh}}{{Si,Ge}} systems at 870 K

Abstract Physico-chemical analysis techniques, including X-ray phase analysis and electron probe X-ray analysis were employed in constructing the isothermal cross-section of the phase diagrams Sm{{Ru,Rh}}{{Si,Ge}} systems at 870 K. The formation of the new ternary intermetallic compounds, Sm2RuGe2, Sm2RhGe2 (structure type Zr2CoSi2); Sm3Ru2Si2, Sm3Rh2Si2, Sm3Rh2Ge2 (structure type La3Ni2Ga2); SmRh5Si3, SmRh5Ge3 (structure type UCo5Si3); Sm2Ru3Si5 (structure type Sc2Fe3Si5); SmRu3Si2 (structure type LaRu3Si2); SmRuSi3 (structure type BaAl4); Sm33Rh20Ge47 (structure type AlB2); Sm25Rh19Ge56 (structure type CeRh1 − xGe2 + x); Sm2RhGe6 (structure type Ce2CuGe6) and Sm62Ru28Ge10, SmRu3Si, Sm2RuSi2. Sm62Ru10Si28, Sm33Rh50Si17, Sm16Rh68Si16, SmRh3Si6, Sm37Rh35Si28, Sm2RhSi2, Sm4Rh4Si, Sm33Rh53Ge14, SmRh2Ge, Sm18Rh64Ge18, SmRh3Ge6, were detected in Sm(Ru,Rh)(Si,Ge) systems. It was found that compound SmRuSi does not belong to the structure type PbFCl. Ternary compound SmRuGe was not found in SmRuGe system at 870 K.

New Ternary Compounds R117Fe52Ge112 (R = Gd, Dy, Ho, Er, Tm) and Sm117Cr52Ge112 of the Tb117Fe52Ge112-Type Structure

Abstract The new compounds Gd117Fe52Ge112 [a = 2.8711(4) nm], Dy117Fe52Ge112 [a = 2.8398(5) nm], Ho117Fe52Ge112 [a = 2.8293)(5) nm], Er117Fe52Ge112 [a = 2.8108(7) nm], Tm117Fe52Ge112 [a = 2.802(2) nm], and Sm117Cr52Ge112 [a = 2.9098(6) nm] belonging to the Tb117Fe52Ge112-type structure (space group Fm3m) were prepared and characterized using powder X-ray diffraction.

New Zr6CoAs2-type R6FeBi2 (R=Y, Lu, Gd–Dy, Er, Tm) compounds

Powder X-ray diffraction investigations of new ternary Zr6CoAs2-type R6FeBi2 (R=Y, Lu, Gd–Dy, Er, Tm) compounds are reported. The compounds Y6FeBi2 (a=0.8265(1) nm, c=0.4214(1) nm), Lu6FeBi2 (a=0.8059(2) nm, c=0.4116(1) nm), Gd6FeBi2 (a=0.8343(2) nm, c=0.4227(1) nm), Tb6FeBi2 (a=0.8281(2) nm, c=0.4194(1) nm), Dy6FeBi2 (a=0.8229(3) nm, c=0.4173(2) nm), Er6FeBi2 (a=0.8161(2) nm, c=0.4153(1) nm) and Tm6FeBi2 (a=0.8112(3) nm, c=0.4135(2) nm) crystallize in the hexagonal Zr6CoAs2-type structure (space group P6b2m No. 189). The Zr6CoAs2-type structure is a superstructure of the Fe2P-type structure.

GdTiGe (CeScSi-type structure) and GdTiGe (CeFeSi-type structure) as the coherent phases with different magnetic and hydrogenization properties

Abstract The results of investigations of new ternary coherent GdTiGe compounds and corresponding hydrides by X-ray powder diffraction and magnetic measurements are reported. Coherent phases GdTiGe with CeScSi-type structure and GdTiGe with CeFeSi-type structure were found to coexist in the GdTiGe alloy when the sample mass was 5 g (melting in electric arc furnace in argon atmosphere). Annealing at 1070 K for 200 h in argon atmosphere led to an increase in GdTiGe (CeScSi-type structure) phase in the GdTiGe alloy. The GdTiGe with CeScSi-type structure ( a = 0.4065(1), c = 1.5450(1) nm) was characterized by Curie point T c = 376 K, while GdTiGe with CeFeSi-type structure ( a = 0.4065(1), c = 0.7716(1) nm) demonstrated Neel point T N = 412 K. The mechanical hydrogenization of the GdTiGe alloy led to formation of the GdTiGeH ∼4 hydride with CeScSi-type structure and to a sharp decrease in magnetization; GdTiGe with CeFeSi-type structure remained passive. The X-ray single crystal diffraction study confirmed that the Gd(Ti 0.8 Zr 0.2 )Ge compound has the CeScSi-type structure (space group I 4/ mmm , a = 0.4060(1), c = 1.5400(3) nm).

Sm-Ru-Ge system at 1070 K

Abstract Phase equilibria in the Sm–Ru–Ge system were investigated by X-ray powder diffraction and the isothermal section at 1070 K was obtained. We confirmed the compounds CeGa 2 Al 2 -type SmRu 2 Ge 2 [ a =0.4229(1) nm, c =0.9933(2) nm, space group I 4 mmm , No. 139], Y 3 Co 4 Ge 13 -type Sm 3 Ru 4 Ge 13 [ a =0.9016(1) nm, space group Pm 3 n , No. 223], La 3 Ni 2 Ga 2 -type Sm 3 Ru 2 Ge 2 [ a =0.5620(1) nm, b =0.7808(1) nm, c =1.3567(2) nm, space group Pbcm , No. 57], U 2 Co 3 Si 5 -type Sm 2 Ru 3 Ge 5 [ a =0.9878(6) nm, b =1.2437(8) nm, c =0.5791(4) nm, space group Ibam , No. 72] and Zr 2 CoSi 2 -type Sm 2 RuGe 2 [ a =1.0948(3) nm, b =1.0839(3) nm, c =0.4302(1) nm, γ =123.23(2)°, space group B 2/ m , No. 12-1]. We found the following new compounds: TiNiSi-type SmRuGe [ a =0.7165(1) nm, b =0.4476(1) nm, c =0.7152(1) nm, space group Pnma , No. 62], CeRh 1− x Ge 2+ x -type Sm 2 RuGe 5− x [ a =0.4061(2) nm, b =0.4179(2) nm, c =1.6226(7) nm, space group Pmmn , No. 59-2], Cr 5 B 3 -type Sm 5 Ru 2 Ge [ a =0.7736(4) nm, c =1.3426(8) nm, space group I 4/ mcm , No. 140] and Tb 3 Co 2 Ge 4 -type Sm 3 Ru 2 Ge 4 [ a =1.0899(9) nm, b =0.8139(8), c =0.4319(3) nm, γ =109.29(7)°, space group B 2/ m , No. 12-1]. The melting temperature for Sm 2 Ru 3 Ge 5 [ T m =1760(10) K], Sm 3 Ru 4 Ge 13 [ T m =1600(10) K], Sm 3 Ru 2 Ge 2 [ T m =1560(10) K] and Sm 2 RuGe 2 [ T m =1750(10) K] were measured.