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1.
The HfFe 6Ge 6-type YbMn 6Ge 6−xGa x solid solution (0.07≤ x≤0.72) has been studied by X-ray diffraction, microprobe analysis and powder magnetization measurements. All the compounds order antiferromagnetically between TN=481 K for x=0.07 and TN=349 K for x=0.72 and display more or less pronounced spontaneous magnetization at lower temperature. The corresponding Curie points increase from 40 K for x=0.07 to 319 K for x=0.72. The maximum magnetization values of the Ga-rich compounds ( M≈5 μB/f.u. at 6 K) is compatible with a ferrimagnetic order of the Mn and Yb sublattices whereas the smaller values measured in the Ga-poor compounds suggest the stabilization of non-colinear magnetic structures. All the studied compounds are characterized by rather large coercive fields at low temperature (4.0≤ Hc≤8.2 kOe). 相似文献
2.
The structure and magnetic properties of the Pr 1−xGd xMn 2Ge 2 (0.0≤ x≤1.0) compounds have been investigated by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC) techniques and AC magnetic susceptibility measurements. All compounds crystallize in the ThCr 2Si 2-type structure with the space group I4/ mmm. The lattice constants and the unit cell volume obey Vegard’s law. Samples in this alloy system exhibit a crossover from ferromagnetic ordering for PrMn 2Ge 2 to antiferromagnetic ordering for GdMn 2Ge 2 as a function of Gd concentration x. At low temperatures, the rare earth sublattice also orders and reconfigures the ordering in the Mn sublattice. The results are summarized in the x– T magnetic phase diagram. 相似文献
3.
Investigations were made by neutron diffraction on Zr 6CoAs 2-type (space group no. 189) Ho 6−xEr xMnBi 2 solid solutions. The ferromagnetic ordering temperature decreases from Ho 6MnBi 2 ( TC = 200(6) K) to Er 6MnBi 2 ( TC = 100(4) K), whereas temperatures of ferrimagnetic (or antiferrimagnetic) ordering ( TFerri and TAFerri) are found to have non-monotonic dependences on the content of Er: TFerri = 58(4) K for Ho 6MnBi 2, TFerri = 162(4) K for Ho 4.5Er 1.5MnBi 2, TFerri = 150(4) K for Ho 3Er 3MnBi 2, TAFerri = 78(4) K for Ho 1.5Er 4.5MnBi 2 and TAFerri = 52(4) K for Er 6MnBi 2. In these compounds, no local moment was detected on the manganese ion site, except for Ho1.5Er4.5MnBi2 and Er6MnBi2 compounds. The manganese magnetic moments (μMn) is 1.5μB and these are antiferromagnetically coupled with that of rare earth moments. 相似文献
4.
Neutron diffraction measurements have been performed on the ternary compounds YMn 6Ge 6 and LuMn 6Sn 6 of HfFe 6Ge 6-type structure (space group, P6/mmm). This structure can be described as a filled derivative of the CoSn-B35-type structure. Each of the rare earth (R) and Mn atoms are successively distributed in alternate layers, stacked along the c axis with the sequence Mn---R---Mn---Mn---R---Mn. At 300 K, both compounds exhibit collinear antiferromagnetic arrangements and the magnetic structures consist of a stacking of ferromagnetic (001) layers of Mn with the coupling sequence Mn(+)---R---Mn(−)---Mn(−)---R---Mn(+) (μ Mn ≈ 1.33(1)μ B and 1.82(3)μ B for LuMn 6Sn 6 and YMn 6Ge 6 respectively). For LuMn 6Sn 6, the magnetic moments lie in the (001) plane, while they are along the c axis in YMn 6Ge 6. At low temperature, a spin reorientation process occurs in both compounds, yielding incommensurate antiferromagnetic arrangements. For YMn 6Ge 6 ( Tt ≈ 80 K), the Mn moments form a double-cone structure with a periodicity of about 105 Å (μ Mn = 1.95(4)μ B at 2 K), while only preliminary results are available for LuMn 6Sn 6 below about 200 K. The results are compared with those obtained on the CoSnB35-type structure binary compounds FeSn and FeGe, on one hand, and the RMn 6Sn 6 compounds, on the other hand. 相似文献
5.
The magnetic properties of ThCr 2Si 2-type structure LaMn 2Ge 2 and LaMn 2Si 2 compounds have been reinvestigated by neutron diffraction experiments. The ferromagnetic ordering previously proposed to take place on the manganese sublattice is revised. At high temperature, both compounds are purely collinear antiferromagnets (not detected by magnetic measurements), characterized by a stacking of antiferromagnetic (001) Mn planes. Below Tc=310 and 325 K for LaMn 2Ge 2 and LaMn 2Si 2, respectively, both compounds exhibit an easy-axis ferromagnetic behaviour. However, the occurrence of a dominant antiferromagnetic component within the (001) Mn planes yields a conical magnetic structure for the germanide (cone semi-angle =58° at 2 K) and a canted magnetic structure for the silicide (φ=49°). At 2 K, the total Mn moments are about 3.0 and 2.4 μ B for LaMn 2Ge 2 and LaMn 2Si 2, respectively. The results are compared with those of closely related RMnSi and RMnGe compounds and the magnetic properties of the ThCr 2Si 2-type structure RMn 2X 2 (XSi, Ge) compounds are discussed. 相似文献
6.
The HfFe 6Ge 6-type RMn 6Sn 6−xX x′ solid solutions (R=Tb, Dy, X′=Ga, In; x≤1.4) have been studied by powder magnetization measurements. All the series are characterized by ferrimagnetic ordering and by a decrease in Curie temperatures with the substitution (Δ Tc/Δ x≈−39 K for X′=Ga and Δ Tc/Δ x≈−75 K for X′=In). The RMn 6Sn 6−xGa x systems are characterized by a strong decrease in the spin reorientation temperature with substitution (Δ Tt/Δ x≈−191 K and −78 K for R=Tb and Dy, respectively) while this transition almost does not change in systems containing indium. The coercive fields drastically decrease with the substitution in the TbMn 6Sn 6−xGa x system while the substitution of In for Sn has a weaker effect. The coercive fields of the Dy compounds do not vary greatly with the substitution in both series. The behaviour of the TbMn 6Sn 6−xGa x is compared with the evolutions observed in the TmMn 6Sn 6−xGa x series. This comparison strongly suggests that the replacement of Sn by Ga changes the sign of the A 02 crystal field parameter. 相似文献
7.
Single crystals of UNi 0. 5Sb 2 were investigated by means of Seebeck coefficient and Hall effect measurements in the temperature range 5–300 K. The results corroborated the occurrence of two magnetic phase transitions: from para- to antiferromagnetic state at TN = 161.5 K and a spin-reorientation near Tt = 64 K. The first-order character of the latter feature was proved by studying in detail the electrical resistivity and the magnetic susceptibility of single-crystalline UNi 0. 5Sb 2 in the vicinity of Tt. 相似文献
8.
Magnetic properties and magnetocaloric effects of Pr 6Co 1.67Si 3 compound have been investigated by magnetization measurements. The saturation moment at 5 K is found to be 10.7 μB. The compound undergoes two magnetic transitions below Curie temperature TC = 48 K and shows a reversible second-order magnetic transition around TC. A magnetic entropy change Δ S = 6.9 J/(kg K) is observed for a magnetic field change from 0 to 5 T. The full width at half maximum of the Δ S peak is found to be about 38 K. 相似文献
9.
The magnetic properties of ThCr 2Si 2-type structure CaMn 2Ge 2 and BaMn 2Ge 2 compounds have been investigated by neutron diffraction experiments. In the whole temperature range studied (2–270 K), both compounds are purely collinear antiferromagnets (not detected by bulk magnetometric measurements) characterized by a stacking of antiferromagnetic (001) Mn planes. This peculiar Mn-sublattice magnetic behaviour seems to be related to the valency of the large metal. At 2 K, the total Mn moments are about 2.7 μ B and 3.6 μ B for CaMn 2Ge 2 and BaMn 2Ge 2, respectively. The results are compared with those of closely related RMnSi and RMnGe compounds and the isotypic alkali-metal manganese pnictides. The magnetic properties of the ThCr 2Si 2-type structure RMn 2X 2 (XSi, Ge) compounds are discussed. 相似文献
10.
The crystal structure of intermetallic compound Gd 6Cr 4Al 43 has been investigated by means of X-ray diffraction data (Ho 6Mo 4Al 43 structure type, space group P6 3/ mcm, Pearson symbol hP106, a = 10.9144(7) Å, c = 17.7361(13) Å). SQUID magnetic measurements carried out for the title compound point to the existence of two antiferromagnetic phase transitions observed at TN1 = 19.0(1) K and TN2 = 6.8(1) K, respectively. 相似文献
11.
The compounds RMn 2Ge 2 (R = Tb, Ho, Er, Tm, Lu) have been investigated by neutron diffraction. TbMn 2Ge 2 is a collinear ferrimagnet with the Mn and Tb moment aligned along the c axis (μ TB = 8.81(59) μ B: μ Mn = 2.21(44) μ B). HoMn 2Ge 2 exhibits incommensurale ordering below 2.1 K characterized by two wavevectors at 1.3 K: q1 = (0.1543(4), 0.1543(4), 0) and q2 = (0.210(1), 0.007(1), 0). The Mn sublattice remains antiferromagnetic down to 1.3 K (μ Mn = 2.38(6) μ B). The Er moments order ferromagnetically below 5.5 K in ErMn 2Ge 2 (μ Mn = 6.81(31) μ B). The moments are perpendicular to the c axis. The Mn sublattice remains antiferromagnetic down to 1.8 K (μ Mn = 2.34(18) μ B). The magnetic structure of TmMn 2Ge 2 is characterized by the propagation vector (0.0.1/2). the Tm moments lying in the basal plane. The ordering of the Tm moments yields a canting of the Mn moments (τ = 21(3)°); μ Tm = 6.63(18) μ B; μ Mn = 2.28(27) μ B). The antiferromagnetic structure of LuMn 2Ge 2 has been determined (μ Mn = 2.32(14) μ B). The evolution of the magnetic properties of the heavy rare earth compounds RMn 2Ge 2 is discussed. 相似文献
12.
The Gibbs free energy of formation of Nd 3RuO 7(s) has been determined using solid-state electrochemical cell employing oxide ion conducting electrolyte. The electromotive force (e.m.f.) of the following solid-state electrochemical cell has been measured, in the temperature range from 929.3 to 1228.6 K. Cell: (−)Pt/{Nd3RuO7(s) + Nd2O3(s) + Ru(s)}//CSZ//O2(p(O2) = 21.21 kPa)/Pt(+) The Gibbs free energy of formation of Nd3RuO7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given by: {ΔfG°(Nd3RuO7, s)/(kJ mol−1) ± 1.6} = −3074.3 + 0.6097(T/K); (929.3 ≤ T/K ≤ 1228.6). The uncertainty estimate for ΔfG°(T) includes the standard deviation in e.m.f. and the uncertainty in the data taken from the literature. The intercept and the slope of the above equation correspond to the enthalpy of formation and entropy, respectively, at the average experimental temperature of Tav. = 1079 K. 相似文献
13.
Gd 5Si 2Ge 2 parent compounds were alloyed with Mn in order to understand the underlying relation between the structural phases and the magnetic behavior of the pseudo ternary compounds formed. The alloying mechanism in Gd 5Si 2Ge 2 causes simultaneous substitution of the nonmagnetic Si and Ge atoms from the (Si + Ge) sublattice in equal amounts. No subsequent heat treatment was made on alloyed compounds. X-ray powder diffraction, magnetization versus temperature and isothermal magnetization measurements were carried out. X- ray diffraction patterns were used to qualitatively determine the existence of different structural phases in the alloys. It was observed that the starting, as-melted alloy with z = 0 has Gd 5Si 4-type orthorhombic structure at room temperature with traces of 1:1 stoichiometry phase which transforms totally to a Gd 5Si 2Ge 2-type monoclinic phase when heat treated. Similarly, increase in the Mn content leads to an increase in the monoclinic phase content of the originally orthorhombic compounds. Curie temperatures were determined from M( T) measurements and the magnetocaloric characterization was made using M( H) measurements by plotting the magnetic entropy change values against temperature. No giant magnetocaloric effect was observed for non heat treated samples. 相似文献
14.
X-ray diffraction, Mössbauer spectroscopy and magnetization measurements were used to study the structure and some magnetic properties of Fe 50Ge 50 and Fe 62Ge 38 prepared by mechanical alloying from the elemental powders. In both cases in the early stages of milling the intermediate paramagnetic FeGe 2 phase was formed. The mechanical alloying process of Fe 50Ge 50 resulted in the formation of the paramagnetic FeGe (B20) phase with an average crystallite size of about 15 nm. In the case of the Fe 62Ge 38, the ferromagnetic Fe 5Ge 3 (β) phase with a Curie temperature of about 430 K was obtained. The average crystallite size was about 9 nm. The average hyperfine magnetic field of about 16 T allowed it to determine that more than four germanium atoms exist in the nearest environment of the 57Fe isotopes in the Fe 5Ge 3 phase. 相似文献
15.
The nature of the magnetic ordering of Tb 4Sb 3 compound (Th 3P 4-type, cubic; cI28, space group , No. 220, a = 0.91518(7) nm) has been investigated by using the techniques of magnetization and neutron diffraction. AC and DC magnetisation measurements indicate antiferromagnetic ordering at 108 K in zero magnetic field that is accompanied by a field-induced metamagnetic transition to a ferromagnetic state, in fields above 0.3 T. Neutron diffraction experiment in zero applied magnetic field shows that below TN = 112(4) K Tb 4Sb 3 exhibits an antiferromagnetic flat spiral-type ordering with propagation vector K 1 = [±1/8, ±1/8, ±1/8]. The magnetic moment of Tb atoms is found to be MTb = 6.7(3) μ B at 80 K. The magnetic moment of Tb atoms lie in the (1 1 1) plane of Tb 4Sb 3 unit cell (the cone axis arranges along [1 1 1] direction with cone angle β = 90°). Below TN2 50 K, Tb 4Sb 3 shows second antiferromagnetic transition with K 2 = [1/2, 1/2, 1/2] with possible re-orientation of Tb magnetic moments. 相似文献
16.
A study of phase relationships and crystallography in the pseudobinary system Gd 5(Si xGe 1−x) 4 revealed: (1) that both terminal binary compounds Gd 5Si 4 and Gd 5Ge 4 crystallize in the Sm 5Ge 4-type orthorhombic structure, and (2) the appearance of an intermediate (ternary) phase with a monoclinic crystal structure which is similar to both Gd 5Si 4 and Gd 5Ge 4. The formation of the monoclinic phase at 0.24≤ x≤0.5 [between Gd 5(Si 0.96Ge 3.03)Gd 5(Si 1Ge 3) and Gd 5(Si 2Ge 2)] is probably due to the large difference in bonding characteristics of Si and Ge in the Gd 5Si 4-Gd 5Ge 4 pseudobinary system which limits the ability of the mutual substitution of Si for Ge and vice versa without a change of the crystal structure. For the composition Gd 5(Si 2Ge 2) the lattice parameters of the monoclinic structure (space group P112 1/a) are a=7.580865), b=14.802(1), c=7.7799(5)Å, γ=93.190(4)°. A distinct difference in the magnetic behaviors of the alloys from three different phase regions in this system follows the distinct difference in the crystal structures observed for the alloys from the three phase regions. 相似文献
17.
In our investigation of non-centrosymmetric rare earth sulfides in the La 3AgSnS 7/KBr, LaAlGeS 5/NaBr, HoAlGeS 5/KBr, ErAlGeS 5/NaBr, Er 3AgGeS 7/KBr and La 3NaSnS 7/NaBr systems, five compounds belonging to the R 6B 2C 2Q 14 family have been obtained. These compounds crystallize in the P6 3 space group, and the crystal data are as follows—La 3AgSnS 7: a = 10.3780(15) Å, c = 5.9900(12) Å, Z = 2; La 3Ge 0.25GeS 7: a = 10.2970(15) Å, c = 5.8120(12) Å, Z = 2; Ho 3Ge 0.272(10)GeS 7: a = 9.6480(14) Å, c = 5.7920(12) Å, Z = 2; Er 3Ge 0.330(10)GeS 7: a = 9.5930(14) Å, c = 5.8490(12) Å, Z = 2; La 3Sn 0.25SnS 7: a = 10.2770(15) Å, c = 6.0030(12) Å, Z = 2. Single-crystal analysis indicated that the crystal structures consist of three types of building block: LnS n, MS 4, and AgS 3 (for La 3AgSnS 7) or MS 6 units (for Ln 3M xMS 7, Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2), as any other compounds belonging to the R 6B 2C 2Q 14 family. Ln 3M xMS 7 (Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2) are deficient compounds with the B sites occupied partly by M(II), and/or M(IV). 相似文献
18.
In our investigation of Co-rich alloys in the ternary U–Co–Sn system, we have identified three intermetallic compounds with composition UCo 2Sn, UCo 4Sn and UCo 5Sn, respectively. The existence and the crystal structure of the first compound, already known in the literature, have been confirmed, while the latter two compounds have been identified for the first time. The crystal structure of these compounds was determined by X-ray diffraction methods, performed both on powders (all samples) and single crystals (UCo 4Sn and UCo 5Sn). The crystal data are as follows (lattice constants from Guinier powder patterns): UCo 2Sn [UPd 2Sn-type, orthorhombic, oP16- Pnma, a = 9.402(3), b = 4.321(1), c = 6.615(2) Å], UCo 4Sn [MgCu 4Sn-type, cubic, , a = 6.992(2) Å] and UCo 5Sn [CeCu 4.38In 1.62-type, orthorhombic, oP56- Pnnm, a = 10.250(1), b = 16.012(2), c = 4.837(1) Å]. The physical properties of the compounds have been studied by electric transport (1.5–300 K), heat capacity (1.8–40 K) and magnetic measurements (1.8–300 K). The magnetisation data reveal weakly paramagnetic behaviour (with weak low temperature upturn due to parasitic impurity phases) in all the three alloys and absence of long-range magnetic ordering, despite the presence of uranium and a substantially high concentration of cobalt. The results for UCo 2Sn are in agreement with earlier reports in the literature. The magnitudes of the coefficients of the linear term in the heat capacity and the T2 term in the low temperature resistivity track the room temperature magnetisation. 相似文献
19.
Structure and magnetic and electrical properties of the polycrystalline compounds LaMn 1−xRh xO 3 (0 < x ≤ 1) have been investigated. The samples were characterized by X-ray diffraction and Rietveld refinement which confirmed the space group Pnma (No. 62) for all compositions at room temperature. A transformation from O′- to O-type orthorhombic structure is seen near x = 0.6 tending to make the phase unstable. The electrical conductivity measurement shows semiconducting property above room temperature with a rather low activation energy for Mn-rich compositions. Compounds in the region 0.1 ≤ x ≤ 0.9 show ferromagnetic property but the substitution of Rh 3+ ion for Mn 3+ ion suppresses the ferromagnetism that results in reducing the Curie temperature, TC. 相似文献
20.
DSC was used to investigate phase equilibrium in the CeBr 3–MBr (M = Li, Na) systems. They represent typical examples of simple eutectic systems. The eutectic composition and eutectic temperature, x(CeBr 3) = 0.249, Teut = 709 K and x(CeBr 3) = 0.372, Teut = 692 K, were found for CeBr 3–LiBr and CeBr 3–NaBr systems, respectively. The electrical conductivity of CeBr3–MBr liquid mixtures, together with that of pure components was measured down to temperatures below solidification. Results obtained are discussed in term of possible complex formation. 相似文献
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