Subsolidus phase relations in the Na2MoO4-CoMoO4-Cr2(MoO4)3 system

Triple molybdate NaCoCr(MoO₄)₃, a phase of variable composition Na₂MoO₄-CoMoO₄-Cr₂(MoO₄)₃ (0 ≤ x ≤ 0.5) having nasicon structure (space group R $ \bar 3 $ \bar 3 c), and triple molybdate NaCo₃Cr(MoO₄)₅ crystallizing in triclinic space group P $ \bar 1 $ \bar 1 were synthesized in the subsolidus region of the Na₂MoO₄-CoMoO₄-Cr₂(MoO₄)₃ ternary salt system. Crystal parameters were calculated for the newly synthesized molybdates and phases. The vibration spectra of Na_{1 − x} Co_{1 − x} Cr_{1 + x} (MoO₄)₃ and electrophysical properties were studied. Upon Na + Co → Cr(III) substitution, chromium cations are distributed to cobalt sites and additional vacancies are generated in the sodium sublattice.     

Interactions in the subsolidus region of the Na2MoO4-NiMoO4-Fe2(MoO4)3 system

Phase relations have been investigated in the subsolidus region of the Na₂MoO₄-NiMoO₄-Fe₂(MoO₄)₃ system by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy. The phase of variable composition Na_1−x Ni_1−x Fe_1+x (MoO₄)₃(0≤x≤0.5) with the NASICON structure (space group R c) and the NaNi₃Fe(MoO₄)₅ ternary molybdate crystallizing in the triclinic crystal system (space group P ) have been obtained. A high conductivity was found in Na_1−x Ni_1−x Fe_1+x (MoO₄)₃, which allows one to consider this phase of variable composition as a promising solid electrolyte with sodium ion conduction. Original Russian Text ? N.M. Kozhevnikova, A.V. Imekhenova, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 4, pp. 695–700.     

Homogeneity regions of double molybdates in the Na2MoO4-MgMoO4 system and structures of triclinic Na1.51Mg2.245(MoO4)3 and Na1.66Mn2.17(MoO4)3

In the samples of the Na₂MoO₄-MgMoO₄ system quenched in the air at above 600°C, by powder X-ray diffraction two double molybdates of variable composition are detected: monoclinic alluaudite-like Na_4?2x Mg_1+x (MoO₄)₃ (0.05 ≤ x ≤ 0.35) and triclinic Na_2?2y Mg_2+y (MoO₄)₃ (0.10 ≤ y ≤ 0.40) isostructural to previously studied Na₂Mg₅(MoO₄)₆. Sodium-magnesium molybdate of the Li₃Fe(MoO₄)₃ structure type is not revealed in this system. By spontaneous flux crystallization, the crystals are obtained and the structures of two triclinic double molybdates of the Na₂Mg₅(MoO₄)₆ structure type (space group $P\bar 1$ , Z = 1) containing magnesium and manganese are determined. The results of the refinement of site occupancies made it possible to determine the composition of the studied crystals: for the compound with magnesium (Na)_0.5(Na_0.255□_0.745)(Na_0.755Mg_0.245)Mg₂(MoO₄)₃ or Na_1.51Mg_2.245(MoO₄)₃ (a = 6.9577(1) Å, b = 8.6330(2) Å, c = 10.2571(2) Å, α = 106.933(1)°, β = 104.864(1)°, γ = 103.453(1)°, R = 0.0188); for the compound with manganese (Na)_0.5(Na_0.33□_0.67)(Na_0.83Mn_0.17)Mn₂(MoO₄)₃ or Na_1.64Mn_2.17(MoO₄)₃ (a = 7.0778(2) Å, b = 8.8115(2) Å, c = 10.4256(2) Å, α = 106.521(1)°, β = 105.639(3)°, Γ = 103.233(1)°, R = 0.0175). The Na₂Mg₅(MoO₄)₆ structure is redetermined and it is shown that actually it corresponds to the composition Na_1.40Mg_2.30(MoO₄)₃.     

Phase equilibrium in the Cs2MoO4-Bi2(MoO4)3-Zn(MoO4)2 system and the crystal structure of new triple molybdate Cs5BiZr(MoO4)6

The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) Å, V = 4138.4(4) ų, Z = 6, space group R $ \bar 3 The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) ?, V = 4138.4(4) ?³, Z = 6, space group R c. The mixed-metal three-dimensional framework in this structure is built of Mo tetrahedra and two sorts of (Bi,Zr)O₆ octahedra. Large interstices accommodate two sorts of cesium atoms. The Bi³⁺ and Zr⁴⁺ cation distributions over two positions were refined during structure solution. Original Russian Text ? B.G. Bazarov, T.V. Namsaraeva, R.F. Klevtsova, A.G. Anshits, T.A. Vereshchagina, R.V. Kurbatov, L.A. Glinskaya, K.N. Fedorov, Zh.G. Bazarova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1585–1589.     

Phase formation in the systems Rb2MoO4-BaMoO4-R2(MoO4)3, R = Nd,Sm, Eu,Gd

Phase formation in the subsolidus area of the systems Rb₂MoO₄-BaMoO₄-R₂(MoO₄)₃ was studied by the methods of X-ray and differential-thermal analysis. In these systems ternary molybdates RbBaR(MoO₄)₃ crystallizing in the monoclinic crystal system (space group P2_1/n ) are formed. Their crystallographic parameters were calculated, and temperature dependences of the electrical conduction, dielectric permeability, and dielectric loss tangent were studied.     

Phase formation in the Ag2MoO4-CoMoO4-Al2(MoO4)3 system

The subsolidus region of the Ag₂MoO₄-CoMoO₄-Al₂(MoO₄)₃ ternary salt system was studied by X-ray powder diffraction analysis. New compounds Ag_1?x Co_1?x Al_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.4) and AgCo₃Al(MoO₄)₅ were detected to form. The variable-composition phase Ag_1?x Co_1?x Al_{1 + x} (MoO₄)₃ is of the NASICON structure type (space group \(R\bar 3c\) ). AgCo₃Al(MoO₄)₅ crystallizes in the triclinic symmetry (space group \(P\bar 1\) Z = 2) with the unit cell parameters a = 6.9101(6), b = 17.519(1), c = 6.8241(6) Å, α = 87.356(7)°, β = 101.078(7)°, and γ = 91.985(9)°. The compounds are thermally stable until 770–780 and 760°C, respectively.     

Subsolidus phase diagrams of the systems Cs2MoO4-R2(MoO4)3-Zr(MoO4)2, where R = Al, Sc, or In

The systems Cs₂MoO₄?R₂(MoO₄)₃?Zr(MoO₄)₂, where R = Al, Sc, or In, have been investigated in the subsolidus region by X-ray powder diffraction. Quasi-binary joins have been revealed, and triangulation has been carried out. Six new triple molybdates have been prepared with the component ratio equal to 1 : 1 : 1 (mol/mol) (S ₁) and 5 : 1 : 2 (S ₂). The crystal parameters for the 5 : 1 : 2 compounds have been determined, and the electrical properties of the 1 : 1 : 1 compounds have been investigated.     

Synthesis and X-ray crystal structures of bis(3-hydroxy-4-methyl-2(3H)-thiazolethiolato-S 2,O)bis(dimethylsulfoxide-O)M,M = cobalt(II) and nickel(II)

Crystallisation of the divalent nickel and cobalt complexes of 3-hydroxy-4-methyl-2(3H)-thiazolethione (HMTT) from DMSO yields isostructural chelate complexes M(MTT)₂(dmso)₂, M = Co^II/Ni^II. The metal atom adopts distorted octahedral coordination via two bidentate MTT ligands arranged in a trans-conformation and two DMSO molecules coordinated through oxygen. Powder X-ray diffraction (PXRD) and energy-dispersive X-ray (EDX) analysis show that the materials form a continuous solid solution Co _x Ni_1–x (MTT)₂(dmso)₂ over the entire composition range 0 x 1.     

Phase Equilibria in the System CuO-Fe2O3-Sb2O4-O2

Results of X-ray phase analysis were used to construct the phase diagram of the system CuO-Fe₂O₃-Sb₂O₄-O₂ at 1000°C in air. Two Cu_2x Fe_4-3x Sb _x O₆ solid solutions (0 x 0.154 and 0.923 x 1) of, respectively, hematite and bixbyite structure were identified.     

Electrical Properties of Molybdates in the Systems M2MoO4-AMoO4-Zr(MoO4)2

The temperature dependence of conductivity of molybdates in the systems M₂MoO₄-AMoO₄-Zr(MoO₄)₂ was studied. The starting molybdates and molybdates of 5 : 1 : 3 and 1 : 1 : 1 compositions, formed in the systems, exhibit mixed conduction, turning ionic at high temperatures. The sharp bends in linear portions of the temperature dependence of conductivity coincide with the temperatures of polymorphic transitions in the corresponding molybdates.     

Metallreiche Phasen im ternären System Ni-Se-Te

Zusammenfassung Die metallreichen Phasen im System Ni-Se-Te wurden durch Röntgenaufnahmen bei Zimmertemp. und bei höheren Temperaturen sowie durchDTA untersucht. Bei Zimmertemp. wurden im pseudo-binären Schnitt Ni₃(Se_1-x , Te _x )₂ Phasen mit den folgenden Strukturen gefunden: rhomboedrischer Ni₃S₂-Typ fürx=0; tetragonaler (Ni,Fe)₁₁Se₈-Typ für 0,15x0,35; tetragonaler Rickardit-Typ für 0,50x0,80; Überstrukturen des Rickardit-Typs für 0,95x1. Bei höheren Temperaturen verbreitert sich das Homogenitätsgebiet der Phase mit der tetragonalen Rickardit-Struktur. Über 600–770°C tritt im ganzen Gebiet 0x1 eine kubisch.

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Metal-rich phases in the ternary system Ni-Se-Te

The metal-rich phases in the system Ni-Se-Te have been studied by X-ray diffraction at room temperature and elevated temperatures, and byDTA. At room temperature phases with the following structures were found in the pseudo-binary section Ni₃(Se_1-x , Te _x )₂: rhombohedral Ni₃S₂ type forx=0; tetragonal (Ni,Fe)₁₁Se₈ type for 0,15x0,35; tetragonal rickardite type for 0,50x0,80; superstructures of the rickardite type for 0,95x1. At higher temperatures the homogeneity range of the phase with the tetragonal rickardite structure broadens. Above 600–770°C a face-centered cubic phase exists in the whole range 0x1; a model for the structure of this phase is proposed. The compound Ni_2,6Te₂ is orthorhombic at room temperature; it becomes hexagonal at 720°C and disproportionates at 820°C; by partial substitution of Te by Se the hexagonal form is stabilized at room temperature. Similarly, the compound Ni₆Se₅ which is stable above 440°C only, is stabilized at room temperature by partial substitution of Se by Te. The phase Ni₆(Se_1-x , Te _x )₅ decomposes by a peritectoid reaction at 650° (x=0) to 590°C (x=0,3).

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Synthesis and phase formation study in K2MoO4-SrMoO4-R2(MoO4)3 systems (where R = Pr, Nd, Sm, Eu, and Gd)

Subsolidus phase formation in K₂MoO₄-SrMoO₄-R₂(MoO₄)₃ systems, where R = Pr, Nd, Sm, Eu, and Gd, in which KSrR(MoO₄)₃ triple molybdates are formed and crystallize in monoclinic crystal system (space group P2₁/n), have been studied using X-ray powder diffraction, differential thermal analysis (DTA), and vibrational spectroscopy. Unit cell parameters have been determined for these molybdates; their IR and Raman spectra are reported.     

Phase formation in the systems Li2MoO4-K2MoO4-Ln2(MoO4)3 (Ln=La, Nd, Dy, Er) and properties of triple molybdates LiKLn2(MoO4)4

Subsolidus phase relations in the systems Li₂MoO₄-K₂MoO₄-Ln₂(MoO₄)₃ (Ln=La, Nd, Dy, Er) were determined. Formation of LiKLn₂(MoO₄)₄ was confirmed in the systems with Ln=Nd, Dy, Er at the LiLn(MoO₄)₂-KLn(MoO₄)₂ joins. No intermediate phases of other compositions were found. No triple molybdates exist in the system Li₂MoO₄-K₂MoO₄-La₂(MoO₄)₃. The join LiLa(MoO₄)₂-KLa(MoO₄)₂ is characterized by formation of solid solutions.Triple molybdates LiKLn₂(MoO₄)₄ for Ln=Nd-Lu, Y were synthesized by solid state reactions (single phases with ytterbium and lutetium were not prepared). Crystal and thermal data for these molybdates were determined. Compounds LiKLn₂(MoO₄)₄ form isostructural series and crystallized in the monoclinic system with the unit cell parameters a=5.315-5.145 Å, b=12.857-12.437 Å, c=19.470-19.349 Å, β=92.26-92.98°. When heated, the compounds decompose in solid state to give corresponding double molybdates. The dome-shaped curve of the decomposition temperatures of LiMLn₂(MoO₄)₄ has the maximum in the Gd-Tb-Dy region.While studying the system Li₂MoO₄-K₂MoO₄-Dy₂(MoO₄)₃ we revealed a new low-temperature modification of KDy(MoO₄)₂ with the triclinic structure of α-KEu(MoO₄)₂¹ (a=11.177(2) Å, b=5.249(1) Å, c=6.859(1) Å, α=112.33(2)°, β=111.48(1)°, γ=91.30(2)°, space group , Z=2).     

A study of phase formation in the subsolidus region of the system Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MnMoO<Subscript>4</Subscript>-Cr<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Phase relationships in the subsolidus region of the system Na₂MoO₄-MnMoO₄-Cr₂(MoO₄)₃ were studied by means of X-ray diffraction and differential-thermal analyses. The possibility of obtaining a variablecomposition phase Na_1?x Mn_1?x Cr_1+x (MoO₄)₃ (0 ≤ x ≤ 0.5) and ternary molybdate NaMn₃Cr(MoO₄)₅ was examined. The temperature dependence of the conductivity of the phase Na_1?x Mn_1?x Cr_1+x (MoO₄)₃ was analyzed.     

Phase equilibria in the Tl2MoO4-Nd2(MoO4)3-Hf(MoO4)2 system and the crystal structure of double molybdate TlNd(MoO4)2

The Tl₂MoO₄-Nd₂(MoO₄)₃-Hf(MoO₄)₂ system was studied in the subsolidus region using X-ray powder diffraction. New triple molybdates were found to exist in this system: Tl₅NdHf(MoO₄)₆ (5: 1: 2), TlNdHf_0.5(MoO₄)₃ (1: 1: 1), and Tl₂NdHf₂(MoO₄)_6.5 (2: 1: 4). The first TlNd(MoO₄)₂ single crystals were grown from melt solutions with spontaneous nucleation. Their crystal structure was refined from X-ray diffraction data (Bruker X8 Apex automated diffractometer, MoK _α radiation, 386 F(hkl), R = 0.0136). The tetragonal unit cell parameters are as follows: a = 6.3000(2) Å, c = 9.5188(5) Å, V = 377.80(3) ų, Z = 2, ρ_calcd = 5.876 g/cm³, space group P4/nnc. The structure is a framework built of NdO₈ and TlO₈ tetragonal antiprisms linked via shared lateral edges and alternating in the checkerboard order. Layers share oxygen vertices with MoO₄ interlayer tetrahedra and are linked into the framework.     

Phase equilibria in the systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Al, In, Sc, Fe(III)) and the crystal structure of double molybdate RbFe(MoO4)2

The systems Rb₂MoO₄-R₂(MoO₄)₃-Hf(MoO₄)₂ have been investigated in the subsolidus region by X-ray powder diffraction, DTA, and IR spectroscopy. Triple molybdates of the composition 5: 1: 2 are formed in the systems with R = Al, In, Sc, and Fe. Molybdates of composition 5: 1: 3 and 1: 1: 1 are found in the iron(III)-containing system in addition to the 5: 1: 2 molybdate. Single crystals of the double molybdate RbFe(MoO₄)₂, which is formed in the Rb₂MoO₄-Fe₂(MoO₄)₃ system, have been grown. The structure of this double molybdate has been refined using X-ray diffraction data (X8 APEX automated diffractometer, MoK _α radiation, 373 F(hkl), R = 0.0287). The trigonal unit cell parameters are the following: a = b = 5.6655(2) Å, c = 7.5061(4) Å, V = 208.65(1) ų, Z = 1, ρ_calc = 3.670 g/cm³, space group R3m1. The structure is formed by layers of FeO₆ octahedra sharing corners with MoO₄ tetrahedra and RbO₁₂ icosahedra.     

Thermal Expansion of Mixed Zirconium Phosphates

A series of framework phosphates with varied ratio of cations Na_5-2x B _x ^IIZr(PO₄)₃, B^II = Mg, Ca, Sr, Ba (0 x 2) and Na_5-3x Fe _x Zr(PO₄)₃ (0 x 1.33) were synthesized and studied under heating. The coefficients of thermal expansion along crystal axes _a and _c were calculated, and their dependences on the cationic composition (nature and concentration) and on the occupancy of out-of-framework structural positions were established.     

Synthesis and study of RbSrR(MoO4)3 ternary molybdates (R = Nd, Sm, Eu, Gd) with scheelite-like structure

Phase relations in the subsolidus region of the Rb₂MoO₄-SrMoO₄-R₂(MoO₄)₃ systems (where R = Nd, Sm, Eu, Gd) were studied by IR spectroscopy, X-ray diffraction analysis, and differential thermal analysis. RbSrR(MoO₄)₃ ternary molybdates (where R = Nd, Sm, Eu, Gd) with scheelite-like structures belonging to the monoclinic crystal system (space group P21/n) were synthesized. Their unit cell parameters were determined; IR and Raman spectra were characterized.     

Binary molybdates K4M2+(MoO4)3 (M2+=Mg, Mn, Co) and crystal structure of K4Mn(MoO4)3

Binary molybdates K₄M²⁺ (MoO₄)₃ (M²⁺=Mg, Mn, Co) isostructural to triclinic \ga-K₄Zn(WO₄)₃ were synthesized, and optimal conditions for their spontaneous crystallization were found. It was established by XRPA and DTA that at 530°C the structure of the compound with cobalt undergoes a transition to the orthorhombic structure of K₄Zn(MoO₄)₃. The structure of K₄Mn(MoO₄)₃ was determined from single crystal diffraction data (a=7.613, b=9.955, c=10.156 Å,α=92.28,β=106.66,γ=105.58°, Z=2, space group $P\bar 1$ , R=0.030). In this compound, Mn has a higher coordination number (CN=5+1) than that of Zn inα-K₄Zn(WO₄)₃ (CN=4+1). The main structural feature is pairs of MnO₆ octahedra linked by the bridging MoO₄ tetrahedra into ribbons stretching along the a axis. The structure is compared with related structures of binary molybdates and other members of the alluaudite family.     

The antiferromagnetic and ferrimagnetic properties of iron selenides with NiAs-type structure

The magnetic properties of the NiAs-type iron selenides have been investigated by susceptibility measurements between 100 and 450 K. Hexagonal -Fe_1-x Se exhibits both antiferromagnetism and ferrimagnetism depending on composition. For antiferromagnetic alloys with 0.02x0.10 (50.5 to 52.5 at % Se) the transition to the paramagnetic state is assumed to occur in the unstable range between room temperatur and about 573K. Ferrimagnetism is observed at compositions near Fe₇Se₈ (0.10x0.16; 52.5 to 54.3 at % Se) withCurie temperatures varying only slightly with composition. In Fe₇Se₈ the ferriparamagnetic transition is observable at 453 K. The characteristic discontinuities in the magnetization curves of Fe₇Se₈ in both superstructures (3c, 4c) are related to the rotation of the magnetic moments from a direction close to [001] into (001).The antiferromagnetism of Fe_0.89Se (52.8 at % Se) changes abruptly into ferrimagnetism when the temperature is raised above 160 K. The similar abrupt changes of the magnetic susceptibilities in the antiferromagnetic region are possibly associated with a crystallographic transformation. In the range of monoclinic -Fe_1-x Se with 0.24x0.36 (56.8 to 61.0 at % Se) only Fe₃Se₄ is ferrimagnetic above room temperature; alloys containing more selenium are ferrimagnetic far below room temperature. In Fe_0.69Se (59.1 at % Se) the transition from ferrimagnetism to paramagnetism was observed at 145 K. The saturation magnetization and the magnetic moments obtained from neutron diffraction are compared with values calculated from a simple ionic model.

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Die antiferromagnetischen und ferrimagnetischen Eigenschaften von Eisenseleniden mitNiAs-Struktur

Zusammenfassung Die magnetischen Eigenschaften von Eisenseleniden mit NiAs-Struktur wurden mittels Suszeptibilitätsmessungen zwischen 100 und 450 K untersucht. Hexagonales -Fe_1-xSe zeigt abhängig von der Konzentration sowohl Antiferromagnetismus als auch Ferrimagnetismus. In antiferromagnetischen Legierungen mit 0,02x0,10 (50,5 bis 52,5 At % Se) verläuft die Umwandlung in den paramagnetischen Zustand im nichfstabilen Bereich zwischen Raumtemperatur und 573 K. Ferrimagnetismus wurde in der Nähe von Fe₇Se₈ (0,10x0,16; 52,5 bis 54,3 At % Se) beobachtet mitCurietemperaturen, die sich nur wenig mit der Konzentration ändern. Fe₇Se₈ zeigt die ferri-paramagnetische Umwandlung bei 453 K. Die charakteristischen Diskontinuitäten der Magnetisierungskurven von Fe₇Se₈ in beiden Überstrukturen (3fache und 4fachec-Achse) hängen mit der Drehung der magnetischen Momente aus einer [001]-nahen Richtung in die (001)-Ebene zusammen. Der Antiferromagnetismus von Fe_0,89Se (52,8 At % Se) geht bei 160 K sprunghaft in Ferrimagnetismus über. Ähnliche sprunghafte Änderungen der magnetischen Suszeptibilitäten im antiferromagnetischen Bereich sind möglicherweise mit einer kristallographischen Umwandlung verbunden. Im Phasenbereich von monoklinem -Fe_1-x Se mit 0,24x0,36 (56,8 bis 61,0 At % Se) ist einzig Fe₃Se₄ oberhalb Raumtemperatur ferrimagnetisch; Legierungen mit mehr Selen sind weit unterhalb Raumtemperatur ferrimagnetisch. In Fe_0,69Se (59,1 At % Se) wurde der Übergang von Ferri- zu Paramagnetismus bei 145 K beobachtet. Die Sättigungsmagnetisierung und die magnetischen Momente aus Neutronenbeugungsexperimenten wurden mit Werten verglichen, die mit einem einfachen ionischen Modell berechnet wurden.