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A potassium salt of the N2S2O2-coordination Fe(III) anion K[Fe(5Cl-thsa)2] (1) (5Cl-thsa - 5-chlorosalicylaldehyde thiosemicarbazone) is synthesized and characterized structurally and magnetically over a wide temperature range. Two polymorphs of salt 1 characterized by the common 2D polymer nature and assigned to the same orthorhombic Pbcn space group have been identified. The molecular structure of the minor polymorph of 1 was solved and refined at 100, 250, and 300 K is shown to correspond to the LS configuration. The dominant polymorph of 1 features K+ cations disordered over a few crystallographic sites, while the minor polymorph includes fully ordered K+ cations. The major polymorph exhibits a complete three-step cooperative spin-crossover transition both in the heating and cooling modes: The first step occurs in a temperature range from 2 to 50 K; the second abrupt hysteretic step occurs from 200 to 250 K with T1/2 = 230 K and a 6 K hysteresis loop. The third gradual step occurs from 250 to 440 K. According to 57Fe Mossbauer, XRPD, and EXAFS data, the spin-crossover transition for the dominant polymorph is quite peculiar. Indeed, the increase in the HS concentration by 57% at the second step does not result in the expected significant increase in the iron(III)-ligand bond lengths. In addition, the final step of the spin conversion (ΔγHS = 26%) is associated with a structural phase transition with a symmetry lowering from the orthorhombic (Pbcn) to the monoclinic (P21/n) space group. This nontrivial phenomenon was investigated in detail by applying magnetization measurements, electron spin resonance, 57Fe Mossbauer spectroscopy, and DFT calculations. These results provide a new platform for understanding the multistep spin-crossover character in the Fe(III) thsa-complexes and related compounds.

Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N'-bis(3-aminopropyl)ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh4 (1), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh4 (2) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh4 (3). Their crystal structure, dielectric constant (ϵ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex (1) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to sharp spin crossovers from the HS to the HS:LS intermediate phase at 137 K and from the intermediate phase to the LS at 87 K, while complex 3 exhibits only one spin transition from the HS to the HS:LS intermediate phase at 83 K.

A novel sodium bismuth oxo-cuprate phosphate chloride, Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77], containing square-kagome layers of Cu2+ has been synthesized by hydrothermal techniques. The compound crystallizes in the tetragonal space group P4/nmm, a = 10.0176(4), c = 10.8545(6), Z = 2, V = 1089.3(1) A3, R1 = 0.021, wR = 0.053, S = 1.32. Its composite crystal structure includes [O4Cu6Bi]7+ layers, which are formed by the clusters of oxygen-centered tetrahedra [OCu3Bi]. These positively charged two periodic fragments are intercalated in a negatively charged [CuNa6Cl3(PO4)4]7- matrix built by Na-centered polyhedra, PO4 tetrahedra, and CuO4Cl pyramids. The composite character of the crystal structure of Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77], as well as the way of its self-assembly, are discussed in close connection with the sulfohalite Na6ClF(SO4)2 salt. It is shown that the "host-guest" model of the formation of the tetragonal Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77] phase is due to the group-subgroup symmetry relation with the cubic crystal structure of mineral sulfohalite and is also supported by the crystallization condition in excess sodium chloride. The magnetic subsystem of Na6Cu7BiO4(PO4)4[Cl2.23(OH)0.77] is represented by a dense square-kagome network of 2Cu1 and 4Cu2 ions, decorated with weakly bonded Cu3 ions. Measurements of magnetization and heat capacity indicate the absence of long-range order up to 2 K, which makes this compound a candidate for a highly demanded spin liquid.

A novel modification of the KCoPO4, δ-phase has been prepared by hydrothermal synthesis at 553 K. The compound crystallizes in the orthorhombic system with the unit-cell parameters a = 8.5031(8), b = 10.2830(5), c = 54.170(4) A. The crystal structure was determined based on synchrotron low-temperature single-crystal X-ray diffraction data obtained from an inversion twin in the space group P212121 and refined to R = 0.077 for 5156 reflections with I > 3σ(I). The δ-KCoPO4 possesses a new structure type which is based on a framework built from sharing vertices Co- and P-centered tetrahedra. The {CoPO4-}∞ construction of tetrahedra may be described as assembled from networks formed by two topologically diverse six-membered rings of tetrahedra stacked together through vertex-bridging contacts along the a axis. The ratio of the (UUUDDD) and (UUDUDD) rings, where (U) and (D) denote the orientation of the tetrahedra in the six-membered rings up and down relative to the plane grids, is equal to 5:1. The (UUDUDD) rings form bands parallel to the [010] direction each surrounded from both sides along the c axis by slabs of five ribbons width having alternative (UUUDDD) topology. Open in the [100] direction channels incorporate K+ ions; this structural feature permits to suppose ion-conductive and/or electrochemical properties of the title compound. The possible mechanism of the δ → γ phase transition is discussed on the basis of the crystal chemical analysis of the KCoPO4 polymorphs. The title compound orders magnetically at TN = 24.8 K.

The unique family of coordination polymers [Ln4(OH)2(piv)10(H2O)2]∞ of 11 lanthanides (Ln = La-Er) has been prepared by a simple solution method based on controlled hydrolysis. The ribbon-like polymeric structure consisting of connected tetranuclear clusters and supported by pivalate ligands and a framework of H-bonds has been revealed by single-crystal X-ray diffraction. While the compounds demonstrate similar PXRD patterns and unit cell parameters, the joint single-crystal XRD and pair distribution function data suggest the significant local structure change along the lanthanide series. The compounds exist as two packing polymorphs (α and β) with similar ribbon geometry, but different supramolecular arrangement of the ribbons. Dehydration of either polymorph does not disturb the tetranuclear core but leads to a translational symmetry loss along the ribbon and a transformation of the 3D-ordered crystal into a 2D-ordered mesostructure. Rehydration of the mesostructure leads to the β polymorph (except La and Ce), allowing the deliberate switching between the polymorphs via dehydration-rehydration evidenced by means of powder X-ray diffraction, pair distribution function analysis, and density functional theory calculations. Ab initio calculations reveal significant magnetic anisotropy of Ln3+ ions with ferro- and antiferromagnetic interactions within tetranuclear [Ln4(OH)2(piv)10(H2O)2] species. Magnetic susceptibility measurements demonstrated antiferromagnetic coupling, slow magnetic relaxation for Dy, Ho, and Er complexes, and field-induced single-chain magnetism for the Dy compound.

A cell for studying the diffusion of therapeutic medical radionuclides into the macrolayer of the carrier sorbent was fabricated using 3D printing. The diffusion of ultramicroquantities of radium and strontium within a layer of watered hydroxyapatite was investigated. The value of the effective diffusion coefficient obtained using a one-dimensional nonstationary model was (1.0 ± 0.4) × 10–8 cm2/s for Ra and (3.0 ± 0.3) × 10–8 cm2/s for Sr.

The sorption of the actinium(iii) ions as 225,228Ac isotopes on hydroxyapatite (HAP) with various textures was studied. A “reverse” generator using an extraction chromatographic sorbent based on diglycolamide derivative (DGA Resin) was proposed for 228Ac production. The chemical yield of the product was ≥90%. The optimal acidity of the solution during sorption (pH 6–7) and the ratio of solid and liquid phases (20 mg of the sorbent per mL of the solution) were determined in preliminary experiments. The process kinetics is adequately described by pseudo-second-order model. The stationary state is reached rapidly (in 10 min) when a HAP suspension is used, whereas time (20–30 min) is needed for textured samples. The possibility of actinium ion diffusion within the bulk of these samples is shown. The diffusion coefficient of actinium estimated by diffusion in a wet HAP paste layer (one-dimensional model) was (1.0±0.2) • 10−7 cm2 s−1.

The radiation resistance of sorbents AG 50 W-X8, Ac resin, and UTEVA resin in contact with hydrochloric solutions under irradiation with 10 MeV electrons in a wide absorbed-dose range up to 2 MGy w...

Basic copper(ii) dihydroxoborate Cu2{BO(OH)2}(OH)3 contains infinite chains consisting of [CuO4] squares that are linked together by sharing opposite edges, due to which this compound is interesting in terms of low-dimensional magnetism. However, investigations of its physical properties are hindered by difficulties with the preparation of single-phase samples. The synthesis method was optimized, and the factors affecting the formation of a crystalline product were established. The synthesized compound was characterized by X-ray diffraction and IR spectroscopy, and its thermal stability was studied. The crystallite formation from the initially unstructured precipitate is described using scanning electron microscopy. An investigation of the temperature dependence of magnetic susceptibility showed that the magnetic properties of basic copper(ii) borate are well described by the weakly alternating spin-1/2 Heisenberg chain model.

Different schemes and designs of generators of low-temperature hybrid plasma produced by simultaneous ionization of plasma-generating medium by an electron beam with electron energy of 30 keV and an RF discharge (13.56 MHz) are considered. A plasma-chemical reactor designed for hybrid plasma generation is described, and results of spectrometric measurements of its reaction volume are presented. The reactor has been used to prepare biocompartible thin chitosan films. Experiments showed that modification of chitosan films in hybrid oxygen plasma improves their hydrophilic properties and has advantages over modification in RF-discharge or electron beam plasma when they are used separately. The bactericidal effect of the hybrid plasma was found in tests Escherichia coli cultures. Prospects for practical hybrid plasma applications in biology and medicine are discussed.

A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N3O2] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H2DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H4DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(С2Н5ОН)Cl] (1), [Er(DAPMBH)(Н2О)Cl]·2C2H5OH (2), [Er(DAPMBH)(СН3ОН)Cl] (3), [Er(DAPMBH)(СН3ОН)(N3)] (4), [(Et3H)N]+[Er(Н2DAPS)Cl2]− (5), and [(Et3H)N]+[Y0.95Er0.05(Н2DAPS)Cl2]− (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1-6 were studied. The AC magnetic measurements revealed that most of Compounds 1-6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, Ueff ≈ 16–28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1-6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.

The local environment of a novel group of americium (Am3+) complexes with calix[4]arene bearing carbamoylmethylphosphine oxide moieties on the upper rim has been investigated by X-ray absorption spectroscopy. The complexes were obtained by the extraction of americium from aqueous nitric or 2-(1-adamantyl)sulfoacetic acids with the 1,2-dichloroethane solution of this ligand. The correlation of the structures of the obtained complexes with americium distribution coefficients in the corresponding extraction systems is revealed.

Sm2Fe17 –xAlx (x = 0.1, 0.2, 0.3 and 0.4) alloys and alloy-based nitrides were synthesized. The chemical and phase composition, microstructure of cast and homogenized alloys, and the hysteresis properties were studied by scanning electron microscopy, local microanalysis, and X-ray diffraction analysis. It was established that nitriding of pseudobinary Sm2Fe17 –xAlx compounds leads to the increase in lattice parameters and simultaneous increase in the specific saturation magnetization. Mechanical activation processing of the nitriding products revealed the different nature of their magnetic behavior depending on aluminum concentration in the alloys. Mechanical activation leads to the increase in coercive force and simultaneous decrease in the values of specific saturation magnetization and the average size of particles at small content of aluminum (18.6 at %). The coercive force of nitride also increases after mechanical activation at high aluminum content (38.3 at %); however, the specific saturation magnetization also increases. Generally, the increase in aluminum content in Sm–Fe–Al–N alloy leads to the decrease in their hysteresis characteristics after mechanical activation processing.

Phase-pure orthorhombic compositions at a Ln/Mo ratio ∼ 5.2–5.7 (Ln = Gd, Dy, Ho) have been obtained for the first time by prolonged (40–160 h) heat treatment of mechanically activated 5Ln2O3 + 2MoO3 (Ln = Gd, Dy, Ho) oxide mixtures at 1200 °C. Although the starting Ln : Mo ratio was 5 : 1 (Ln10Mo2O21 (Ln = Dy, Ho)), it changed slightly in the final product due to the volatility of molybdenum oxide at 1200 °C (40–160 h) (ICP-MS analysis). Brief high-temperature firing (1600 °C, 3 h) of 5Ln2O3 + 2MoO3 (Ln = Gd, Dy, Ho) oxide mixtures leads to the formation of phase-pure fluorites with compositions close to Ln10Mo2O21 (Ln = Gd, Dy, Ho). Gd10Mo2O21 molybdate seems to undergo an order–disorder (orthorhombic–fluorite) phase transition in the range of 1200–1600 °C. For the first time, using the neutron diffraction method, it was shown that low-temperature phases with a Ln/Mo ratio ∼ 5.2–5.7 (Ln = Gd, Dy, Ho) have an orthorhombic structure rather than a tetragonal structure. Proton contribution to the total conductivity of Ln10Mo2O21 (Ln = Gd, Dy, Ho) fluorites and gadolinium and dysprosium orthorhombic phases in a wet atmosphere was observed for the first time. In both orthorhombic and fluorite phases, the total conductivity in wet air decreases with decreasing lanthanide ionic radii. In a wide temperature range, the compounds under study exhibit paramagnetic behaviour. However, the orthorhombic phases of Dy and Ho compounds reach the antiferromagnetic state at 2.4 K and 2.6 K, respectively.

A series of three mononuclear pentagonal-bipyramidal V(iii) complexes with the equatorial pentadentate N3O2 ligand (2,6-diacethylpyridinebis(benzoylhydrazone), H2DAPBH) in the different charge states (H2DAPBH0, HDAPBH1-, DAPBH2-) and various apical ligands (Cl-, CH3OH, SCN-) were synthesized and characterized structurally and magnetically: [V(H2DAPBH)Cl2]Cl·C2H5OH (1), [V(HDAPBH)(NCS)2]·0.5CH3CN·0.5CH3OH (2) and [V(DAPBH)(CH3OH)2]Cl·CH3OH (3). All three complexes reveal paramagnetic behavior, resulting from isolated S = 1 spins with positive zero-field splitting energy expected for the high-spin ground state of the V3+ (3d2) ion in a PBP coordination. Detailed high-field EPR measurements for compound 3 show that its magnetic properties are best described by using the spin Hamiltonian with the positive ZFS energy (D = +4.1 cm-1) and pronounced dimer-like antiferromagnetic spin coupling (J = -1.1 cm-1). Theoretical analysis based on superexchange calculations reveals that the long-range spin coupling between distant V3+ ions (8.65 A) is mediated through π-stacking contacts between the planar DAPBH2- ligands of two neighboring [V(DAPBH)(CH3OH)2]+ complexes.

The syntheses, structure and magnetic properties are reported for five novel 1D polymeric azido-bridged lanthanide complexes with the general formula {[Ln(DAPMBH)(N3)C2H5OH]C2H5OH}n where H2DAPMBH = 2,6-diacetylpyridine bis(4-methoxybenzoylhydrazone)-a new pentadentate pyridine-base [N3O2] ligand and Ln = Dy (1), Y0.930Dy0.070 (2), Er (3), Y0.923Er0.077 (4), and Gd (5). X-ray diffraction analysis of 1-5 show that the central lanthanide atoms are eight-coordinated with the N5O3 donor set originating from the ligand DAPMBH, one coordinated ethanol molecule and two end-to-end type N3- bridges connecting the metal centers into infinite chain. The [LnN5O3] coordination polyhedron can be regarded as a distorted dodecahedron (D2d). AC magnetic measurements revealed that compounds 1-4 show field-induced single-molecule magnet behavior, with estimated energy barriers Ueff ≈ 47-17 K. The experimental study of magnetic properties was complemented by theoretical analysis based on crystal-field calculations. Direct current magnetic susceptibility studies revealed marginally weak intrachain exchange interaction between Ln3+ ions mediated by the end-to-end azide bridging groups (J ≈ -0.015 cm-1 for 5). Comparative analysis of static and dynamic magnetic properties of magnetically concentrated (1, 3) and diluted (2, 4) Dy and Er compounds showed that, despite fascinating 1D azido-bridged chain structure, compounds 1 and 3 are not single-chain magnets; their magnetic behavior is largely due to single-ion magnetic anisotropy of individual Ln3+ ions.

Single crystals of Rb2CaCu6(PO4)4O2 were synthesized by a hydrothermal method in the multicomponent system CuCl2–Ca(OH)2–RbCl–B2O3–Rb3PO4. The synthesis was carried out in the temperature range from 690 to 700 K and at the general pressure of 480–500 atm [1 atm = 101.325 kPa] from the mixture in the molar ratio 2CuO:CaO:Rb2O:B2O3:P2O5. The crystals studied by single-crystal X-ray analysis were found to be monoclinic, space group C2, a = 16.8913 (4), b = 5.6406 (1), c = 8.3591 (3) Å, β = 93.919 (3)°, V = 794.57 (4) Å3. The crystal structure of Rb2CaCu6(PO4)4O2 is similar to that of shchurovskyite and dmisokolovite and is based upon a heteropolyhedral open framework formed by polar layers of copper polyhedra linked via isolated PO4 tetrahedra. The presence of well-isolated 2D heteropolyhedral layers in the title compound suggests low-dimensional magnetic behavior which is masked, however, by the fierce competition between multiple ferromagnetic and antiferromagnetic exchange interactions. At T C = 25 K, Rb2CaCu6(PO4)4O2 reaches a magnetically ordered state with large residual magnetization.

A novel modification of the CsMnPO4β-phase was achieved by hydrothermal synthesis at 553 K. The compound crystallizes in the monoclinic system with the basic unit-cell parametersa= 11.0699 (4),b= 11.0819 (6),c= 9.1106 (3) Å, γ = 119.480 (5)o; the modulation vectors areq1= 0.4a* andq2= 0.4b*. The structure was determined based on single-crystal X-ray diffraction data obtained from a pseudo-merohedral twin using a superspace approach in the (3 + 2)D symmetry groupP11a(a1,b1,0)0(a2,b2,0)0 and refined toR= 0.083 for 10 266 reflections withI> 3σ(I). It is considered as a low-temperature polymorph of CsMnPO4with the sameUUUDDD-type layer topology built by MnO4and PO4tetrahedra, and stacked in a framework in the same manner as β-tridymite. Large open channels parallel to the [110] and [001] directions incorporate Cs atoms. All Cs atoms are distributed along theasuper= 55.35 (1) andbsuper= 55.41 (1) axes of the large unit cell with pseudo periods ofasuper/5 andbsuper/5 which are broken mainly by the positions of oxygen atoms (orientation of Mn- and P-centered tetrahedra). The β-phase is discussed as a member of the morphotropic series of manganese phosphates with large cations ofAMnPO4, whereA =Cs, Rb, K and Ag. The title compound is an antiferromagnet with the Neel temperatureTN= 4.5 K.

We present herein the synthesis, crystal structure, and electric and magnetic properties of the spin-crossover salt [Mn(5-Cl-sal-N-1,5,8,12)]TCNQ1.5 ⋅2 CH3 CN (I), where 5-Cl-sal-N-1,5,8,12=N,N'-bis(3-(2-oxy-5-chlorobenzylideneamino)propyl)-ethylenediamine, containing distinct conductive and magnetic blocks along with acetonitrile solvent molecules. The MnIII complex with a Schiff-base ligand, [Mn(5-Cl-sal-N-1,5,8,12)]+ , acts as the magnetic unit, and the π-electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ- ) is the conducting unit. The title compound (I) exhibits semiconducting behavior with room temperature conductivity σRT ≈1×10-4 ohm-1 cm-1 and activation energy Δ ≈0.20 eV. In the temperature range 73-123 K, it experiences a hysteretic phase transition accompanied by a crossover between the low-spin S=1 and high-spin S=2 states of MnIII and changes in bond lengths within the MnN4 O2 octahedra. The pronounced shrinkage of the basal Mn-N bonds in I at the spin crossover suggests that the d x 2 - y 2 orbital is occupied/deoccupied in this transition. Interestingly, the bromo isomorphic counterpart [Mn(5-Br-sal-N-1,5,8,12)]TCNQ1.5 ⋅2 CH3 CN (II) of the title compound evidences no spin-crossover phenomena and remains in the high-spin state in the temperature range 2-300 K. Comparison of the chloro and bromo compounds allows the thermal and spin-crossover contributions to the overall variation in bond lengths to be distinguished. The difference in magnetic behavior of these two salts has been ascribed to intermolecular supramolecular effects on the spin transition. Discrete hydrogen bonding exists between cations and cations and anions in both compounds. However, the hydrogen bonding in the crystals of II is much stronger than in I. The relatively close packing arrangement of the [Mn(5-Br-sal-N-1,5,8,12)]+ cations probably precludes their spin transformation.

Binding of bismuth cation with two newly synthesized picolinate containing acyclic (L1) and macrocyclic (L2) ligands was studied. Both ligands demonstrate complex formation with Bi3+ under ambient conditions with high complexation constants. Serum stability of the complexes was investigated in serum protein excess of 10- and 100-times. Experiments with no-carrier-added radiobismuth (207Bi and 213Bi) were performed. A one-column 225Ac/213Bi generator system, based on Ac resin (Triskem Inc.), was tested. The overall yield of 213Bi was exceeding 85% with 225Ac breakthrough below 10−4%.

A scheme of an “inverse” generator based on an inorganic sorbent (annealed zirconium and yttrium mixture oxides) has been proposed and tested. The generator demonstrated high yield of the 213Bi product (up to 97 % in 0.5 mL of eluate), high degree of purification from the actinium isotopes (up to 10−2 % of initial 225Ac in 3 M NaNO3 solution), as well as the products of 227Ac decay, and low radiation impact on the sorbent. Application of circulating approach to the sorption of 213Bi provides decreasing processing time to 5 min at higher yield of the product.

The dynamics of the 223Ra distribution in the volume of spherical hydroxyapatite (HAP) granules in the course of the 223Ra sorption from aqueous solutions onto sorbent particles and desorption was studied by α-track radiography. The optimum time of contact of the sample with a detector (exposure) was found, and a procedure for preparing experimental samples was suggested. Taking into account the density of the porous sorbent, the ranges of the α-particles emitted by 223Ra and its daughter products and of the recoil nuclei were estimated. The averaged effective range of the α-particles in HAP is ∼35 μm. A mathematical model of the Ra diffusion into the depth of the porous sorbent, taking into account the sorption, was developed on the basis of the parameters obtained. The effective diffusion coefficient was estimated at ∼3 × 10–5 cm2 s–1. Correlation be¬tween the sorbent particle size, radionuclide sorption time, and the absorbed dose produced by the particle in a biological tissue was demonstrated.

We report the first four magnetic representatives of the trigonal layered A2M(4+)TeO6 (here, M = Mn) family. Na2MnTeO6 was synthesized from NaMnO2, NaNO3, and TeO2 at 650–720 °C, but analogues for ...

The ability of inorganic hydroxide sorbents Termoxid-5 (T-5) and Termoxid-39 (T-39) heat-treated at temperatures from 100 to 950°C to take up radionuclides of the 225Ac subfamily was examined in a wide range of solution acidities and salt compositions. T-5 and T-39 are principally suitable for the development of both direct and inverse 225Ac/213Bi generators with the activity of hundreds of millicuries of 225Ac.

A new two-column 225Ac/213Bi generator was developed specifically for using 225Ac containing an impurity of long lived 227Ac. The parent 225Ac was retained on the first Actinide Resin column, while 213Bi was accumulated on the second column filled with AG MP-50 resin via continuous elution and decay of intermediate 221Fr. The 213Bi accumulation was realized in circulation mode which allowed a compact generator design. It was demonstrated that 213Bi could be quickly and effectively extracted from AG MP-50 in form of complexes with various chelating agents including DTPA and DOTA. The performance of the generator presented and a conventional single-column generator on the base of AG MP-50 was tested and both generators were loaded with 225Ac containing 227Ac impurity. The 213Bi generation efficiencies were comparable and greater than 70%, whereas the developed generator provided a deeper degree of purification of 213Bi from Ac isotopes and decay products of 227Ac.

Many researchers study the Earth's climate change and the impact of the greenhouse effect on this process. The large amount of methane (CH4) is preserved in permafrost. In this regard, scientists recently pay a great attention to the problem of methane emission during the permafrost degradation in the Arctic zone. Until now, the methane content in underground ice, frozen Quaternary sediments has been studied insufficiently. The methane content in the active layer is especially poorly studied.The authors researched methane content in frozen grounds of the upper permafrost horizon (transition zone) and in thawed sediments of the active layer for different tundra landscapes near the Marre-Sale polar station on the western coast of the Yamal peninsula and for landscapes of the Pechora river estuary area (Russia).More than 420 samples of gas from sediments in active and transient layer were collected in Marre-Sale and 36 samples in Pechora area. To determine the methane content, the samples were placed in syringes and degassed using the “head space” technique. CH4 measurements were carried out on a chromatograph with flame ionization detector (FID) Shimadzu GC-2014 (Japan) in the laboratory of Federal State Institution “VNIIOkeangeologiya” (Saint-Petersburg, Russia).Methane content in the frozen and thawed sediments of different dominant landscapes of typical tundra on Yamal peninsula and landscapes of southern tundra on Pechora area is extremely variable. The greatest amount of methane is typical for the most wet landscapes with primarily of silt loam soils. In dry primarily sandy well-drained landscapes, the methane content is low. The highest methane content is measured within the low floodplain of river, water tracks, swampy depressions of polygonal relief, and lake basins landscapes (mean varied from 0.8 to 2.5 ml [CH4] / kg, with a maximum of 9.0 ml [CH4] / kg). For landscapes of the moist surface of typical tundra, the average values of methane content were approximately 0.4 ml [CH4] / kg (with a maximum of 3.4 ml [CH4] / kg). The lowest methane contents in soils were characteristic of the landscapes of well-drained tundra, and sand fields where the average values do not exceed 0.2 ml [CH4] / kg. Mean methane content in soils of Pechora river mouth landscapes varied from 0.05 to 4.5 ml [CH4] / kg, with a maximum of 15.8 ml [CH4] / kg.Determined that methane contents in the frozen soils of the transition zone is 2 to 5 times higher than in the soils of the active layer. High content of methane in upper layers of permafrost should be considered as a significant source of methane, which can be involved in emission of greenhouse gases into the atmosphere during permafrost degradation.

The use of electrophysical effects for presowing treatment of seeds belongs to most effective methods of improving their sowing quality. However, application of such methods is limited by the fact that specialized new-type technological equipment is normally required for their implementation in seed processing lines. This problem can be solved in a simpler way where processing lines designed for forced ventilation are applied for presowing treatment of grain crops. This work deals with the issues related to the use of aerated bins and convection-type microwave grain driers for presowing processing of seeds.

A new oxide, sodium-iron antimonate, Na2FeSbO5, was synthesized and structurally characterized, and its static and dynamic magnetic properties were comprehensively studied both experimentally by dc and ac magnetic susceptibility, magnetization, specific heat, electron spin resonance (ESR) and Mössbauer measurements, and theoretically by density functional calculations. The resulting single-crystal structure (a = 15.6991(9) Å b = 5.3323 (4) Å c = 10.8875(6) Å S.G. Pbna) consists of edge-shared SbO6 octahedral chains, which alternate with vertex-linked, magnetically active FeO4 tetrahedral chains. The 57Fe Mössbauer spectra confirmed the presence of high-spin Fe3+ (3d5) ions in a distorted tetrahedral oxygen coordination. The magnetic susceptibility and specific heat data show the absence of a long-range magnetic ordering in Na2FeSbO5 down to 2 K, but ac magnetic susceptibility unambigously demonstrates spin-glass-type behavior with a unique two-step freezing at Tf1 ≈ 80 K and Tf2 ≈ 35 K. Magnetic hyperfine splitting of 57Fe Mössbauer spectra was observed below T∗ ≈ 104 K (Tf1 < T*). The spectra just below T∗ (Tf1 < T < T*) exhibit a relaxation behavior caused by critical spin fluctuations, indicating the existence of short-range correlations. The stochastic model of ionic spin relaxation was used to account for the shape of the Mössbauer spectra below the freezing temperature. A complex slow dynamics is further supported by ESR data revealing two different absorption modes presumably related to ordered and disordered segments of spin chains. The data imply a spin-cluster ground state for Na2FeSbO5. © 2019 American Chemical Society.

A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er and 6-Tb complexes) or H2LOCH3, (2-Dy complex) has been synthesized by reaction of two equivalents of 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))dibenzohydrazine (H2LH, [H2DAPBH]) or 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))di-4-methoxybenzohydrazine (H2LOCH3, [H2DAPMBH]) with common lanthanide salts. The terbium complex [Tb(LH)(NO3)(H2O)2](DME)2 (5-Tb) with one ligand H2LH was also obtained and characterized. Single crystal X-ray analysis shows that complexes 1–4 have the composition {[Ln3+(HL)-(L)2-] solv} and similar molecular structures. In all the compounds, the central Ln3+ ion is chelated by two interlocked pentadentate ligands resulting in the coordination number of ten. Each lanthanide ion is coordinated by six nitrogen atoms and four oxygen atoms of the two N3O2 chelating groups forming together a distorted bicapped square antiprismatic polyhedron N6O4 with two capping pyridyl N atoms in the apical positions. The ac magnetic measurements reveal field-induced single-molecule magnet (SMM) behavior of the two dysprosium complexes (with barriers of Ueff = 29 K at 800 Oe in 1-Dy and Ueff = 70 K at 300 Oe in 2-Dy) and erbium complex (Ueff = 87 K at 1500 Oe in 4-Er); complex 3-Ho with a non-Kramers Ho3+ ion is SMM-silent. Although 2-Dy differs from 1-Dy only by a distant methoxy-group in the phenyl ring of the ligand, their dynamic magnetic properties are markedly different. This feature can be due to the difference in long-range contributions (beyond the first coordination sphere) to the crystal-field (CF) potential of 4f electrons of Dy3+ ion that affects magnetic characteristics of the ground and excited CF states. Magnetic behavior and the electronic structure of Ln3+ ions of 1–4 complexes are analyzed in terms of CF calculations.

The coexistence of charge density wave (CDW) and superconductivity in tantalum disulfide (2H-TaS$_2$) at ambient pressure, is boosted by applying hydrostatic pressures up to 30GPa, thereby inducing a typical dome-shaped superconducting phase. The ambient pressure CDW ground state which begins at TCDW = 76 K, with critically small Fermi surfaces, was found to be fully suppressed at Pc = 8.7GPa. Around Pc, we observe a superconducting dome with a maximum superconducting transition temperature Tc = 9.1 K. First-principles calculations of the electronic structure predict that, under ambient conditions, the undistorted structure is characterized by a phonon instability at finite momentum close to the experimental CDW wave vector. Upon compression, this instability is found to disappear, indicating the suppression of CDW order. The calculations reveal an electronic topological transition (ETT), which occurs before the suppression of the phonon instability, suggesting that the ETT alone is not directly causing the structural change in the system. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods and the corresponding lower critical field H$_{c1}$ was deduced. While a d wave and single-gap BCS prediction cannot describe our H$_{c1}$ experiments, the temperature dependence of the H$_{c1}$ can be well described by a single-gap anisotropic s-wave order parameter., 6 Pages, 4 figures

The manganese tellurate ${\mathrm{Li}}_{2}{\mathrm{MnTeO}}_{6}$ consists of trigonal spin lattices made up of ${\mathrm{Mn}}^{4+}$ (${d}^{3}$, $S=3/2$) ions. The magnetic properties of this compound were characterized by several experimental techniques, which include magnetic susceptibility, specific-heat, dielectric permittivity, electron-spin-resonance, nuclear magnetic resonance (NMR), and neutron powder-diffraction measurements, and by density functional theory calculations. The magnetic susceptibility $\ensuremath{\chi}(T)$ demonstrates very unusual behavior. It is described by the Curie-Weiss law at high temperature with Curie-Weiss temperature of $\mathrm{\ensuremath{\Theta}}=\ensuremath{-}74\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and exhibits no obvious anomaly indicative of a long-range magnetic ordering at low magnetic fields. At high magnetic fields, however, the character of $\ensuremath{\chi}(T)$ changes showing a maximum at about 9 K. That this maximum of $\ensuremath{\chi}(T)$ reflects the onset of an antiferromagnetic order was confirmed by specific-heat measurements, which exhibit a clear $\ensuremath{\lambda}$-type anomaly at ${T}_{\mathrm{N}}\ensuremath{\approx}8.5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ even at zero magnetic field, and by $^{7}\mathrm{Li}$ NMR and dielectric permittivity measurements. The magnetic structure of ${\mathrm{Li}}_{2}{\mathrm{MnTeO}}_{6}$, determined by neutron powder-diffraction measurements at 1.6 K, is described by the ${120}^{\ensuremath{\circ}}$ noncollinear spin structure with the propagation vector $\mathbit{k}=(1/3,\phantom{\rule{0.28em}{0ex}}1/3,\phantom{\rule{0.28em}{0ex}}0)$. Consistent with this finding, the spin-exchange interactions evaluated for ${\mathrm{Li}}_{2}{\mathrm{MnTeO}}_{6}$ by density functional calculations are dominated by the nearest-neighbor antiferromagnetic exchange within each triangular spin lattice. This spin lattice is strongly spin frustrated with $f=|\mathrm{\ensuremath{\Theta}}|/{T}_{\mathrm{N}}\ensuremath{\approx}8$ and exhibits a two-dimensional magnetic character in a broad temperature range above ${T}_{\mathrm{N}}$.

A coordination compound with the composition [CoLCl2]·H2O (L = bis-condensation product of diacetyl and 2-hydrazinyl-4,6-dimethylpyrimidine) was synthesized, in which the Co(II) ion was hexacoordinated. Under applied DC fields, this compound exhibited single-ion magnet behavior. Two relaxation processes were observed when increasing the applied magnetic field from 1000 to 3200 Oe. The first relaxation (high-frequency) was observed both at 1000 Oe and 3200 Oe, while the second relaxation was only registered under a field of 3200 Oe at low frequencies (

The iron(iii) complex [Fe(Hsemsal)(semsal)]·3H2O (1) (H2semsal - salicylaldehyde semicarbazone) has been synthesized and characterized by powder and single crystal X-ray diffraction, and magnetic susceptibility measurements. Crystal structure analysis showed that the complex forms neat stacks stabilized by hydrogen-bonding through water molecules and π-π interactions between phenolate rings of ligands. The complex does not exhibit spin-crossover phenomena and remains in the high-spin state down to 2 K. DFT calculations were performed for a series of neutral Fe(iii) complexes, and the influence of the N2S2O2, N2Se2O2 and N2O4 coordination environment on the spin transition in these complexes was traced. The effect of substituents in the benzene ring of salicylaldehyde on the stabilization of the HS or LS states in complexes of this type was analyzed.

The cytotoxicity of complex 69mZnLigCl2 (Lig is N-(5,6-dihydro-4H-1,3-thiazin-2-yl) benzamide) against the K-562 cell line (chronic myeloid leukemia) was considered in comparison with the cells of healthy donors. The 69mZnLigCl2 complex was obtained and characterized by TLC and autoradiography methods. The kinetics of zinc sorption on hydroxyapatite was studied.

We report the first highly conducting single-molecule magnet, (BEDO)4[ReF6]·6H2O [1; BEDO = bis(ethylenedioxo)tetrathiafulvalene], whose conductivity and single-molecule magnetism coexist in the same temperature range. The compound was synthesized by BEDO electrocrystallization in the presence of (Ph4P)2[ReF6]·2H2O and characterized by crystallography and measurements of the conductivity and alternating-current magnetic susceptibility.

Two aluminophosphate analogues of the mineral pollucite with the general formula Cs2(M,Al)3P3O12 (where M = Cu or Mn) have been synthesized by high-temperature flux and structurally characterized using the single-crystal X-ray diffraction. Both samples crystallize in cubic I4132 space group, Z = 8, with a = 13.5911(5) and a = 13.8544(7) for Cu- and Mn-loaded phases, respectively. Their framework structures are based on the ANA-type topology and exhibit the partial ordering of the metal (M/Al) and phosphorus (P) cations over the tetrahedral sites. The regular changes in cell dimensions and volumes in the row Cs2(Cu,Al)3P3O12→Cs2(Mn,Al)3P3O12 obviously correspond to increasing radii of the transition metal. The crystal chemical analysis of both pollucite-like phases show correlations between the difference in the radii size of tetrahedral cations and the degree of distortion of flexible ANA-type framework due to decreasing of the intertetrahedral angles (T–O–T). Magnetic susceptibility measurements indicate that both compounds are paramagnets in the temperature range of 2–300 K.

Novel copper cadmium selenite chloride has been synthesized via vapor transport reaction as well as by solid state process. CdCu2(SeO3)2Cl2 crystallizes in a monoclinic space group I2/a with cell constants a ​= ​7.8057(3) A, b ​= ​9.6036(4) A, c ​= ​10.7817(5) A and β ​= ​102.362(4)°, Z ​= ​4. Its crystal structure can be described as an open channel three-dimensional framework, formed by [CdO2Cl4] and [CuO4Cl2] polyhedra interconnected by pyramidal SeO3 groups. The copper polyhedra form magnetically isolated dimers with a spin gap Δ ​= ​38.7 ​± ​0.8 ​meV, as defined from magnetic susceptibility measurements. The electron band gap estimated by diffuse reflectance method Eg ​= ​2.82 ​± ​0.02 ​eV is in agreement with the yellow-green color of the substance. Density functional theory provides the values of electron (2.4 ​eV) and spin (36.6 ​meV) gaps consistent with experimental observations.

Potassium dimanganese trivanadate, KMn2V3O10, was synthesized hydrothermally and its crystal structure was determined from single-crystal X-ray diffraction data. The novel phase crystallizes with triclinic symmetry in space group P\bar 1 with unit-cell parameters of a = 6.912 (5), b = 6.993 (5), c = 9.656 (5) Å, α = 101.858 (5), β = 102.627 (5), γ = 100.669 (5)°, Z = 2 and V = 432.6 (5) Å3. Its structure is built from tetramers of MnO6 octahedra sharing edges and trimers of VO4 tetrahedra sharing vertices. These main structural fragments are linked in a three-dimensional framework with channels occupied by potassium ions. The transformation of this structure to that of interconnected NaCa3Mn(V3O10)(V2O7) is discussed. The title compound orders antiferromagnetically at T N = 8.2 K due to the magnetic exchange interactions between tetramers of Mn octahedra through VO4 tetrahedra. First-principles calculations show the magnetic couplings via Mn—O—Mn and Mn—O—V—O—Mn pathways.

Four new manganese germanates and silicates, A2MnGeO4 (A = Li, Na) and A2MnSiO4 (A = Na, Ag), were prepared, and their crystal structures were determined using the X-ray Rietveld method. All of them contain all components in tetrahedral coordination. Li2MnGeO4 is orthorhombic (Pmn21) layered, isostructural with Li2CdGeO4, and the three other compounds are monoclinic (Pn) cristobalite-related frameworks. As in other stuffed cristobalites of various symmetry (Pn A2MXO4, Pna21 and Pbca AMO2), average bond angles on bridging oxygens (here, Mn–O–X) increase with increasing A/X and/or A/M radius ratios, indicating the trend to the ideal cubic (Fd3m) structure typified by CsAlO2. The sublattices of the magnetic Mn2+ ions in both structure types under study (Pmn21 and Pn) are essentially the same; namely, they are pseudocubic eutaxy with 12 nearest neighbors. The magnetic properties of the four new phases plus Li2MnSiO4 were characterized by carrying out magnetic susceptibility, specific heat, magnetization, and...

The magnetic properties of 3d-transition metal polyanionic compounds differ markedly from those of the monoanionic compounds. The simplest of them can be considered as systems with structures containing cations of a single metal in the Ti–Cu series and several different anions (F−, Cl−, Br−, (OH)−, O2−). Metal orbitals overlap differently with orbitals of the halogen, hydroxyl groups and oxygen causing a wide spread in competition among the different exchange interactions in polyanionic compounds. At the same time, exchange with other cations, including non-transition metals, does not occur in these compounds. The physics of polyanionic magnets remains largely unexplored, since such systems are usually chemically active and require particular care when physical measurements are made.

The article is devoted to the topical problem of rational use of energy and nutrient content of feed in obtaining livestock products (milk) from cows by shifting the energy balance of the animal’s body towards “productive energy”, i.e. the synthesis of fat and proteins. The authors would like to point out that one of the main factors influencing fluctuations in the energy balance of an animal are microclimate parameters, as the deviation of the microclimate parameters from the established optimal limits leads to a reduction in milk yields by 10 to 20%. Therefore, the aim of our work is to develop an energy-saving technology for the formation of optimal microclimate in livestock facilities using air conditioning systems, which can regulate most of the parameters of the microclimate inside them, namely: temperature, relative humidity and internal air velocity, concentration of harmful gases (carbon dioxide, ammonia, and hydrogen sulfide), dust and microorganisms. The presence of the mode enabling recirculation air purification allows to save heat energy and energy coming with feed by up to 50% compared with typical microclimate systems. To this end, we have systematized separate data from scientific researches done by various scientists in the fields of animal hygiene and veterinary medicine and obtained dependencies of influence of microclimate parameters (temperature, relative humidity, internal air velocity) on the productivity of animals (cows) and feed consumption.

MnSnTeO6, a new chiral antiferromagnet, was prepared both by topotactic transformation of the metastable rosiaite-type polymorph and by direct synthesis from coprecipitated hydroxides. Its structure and its static and dynamic magnetic properties were studied comprehensively both experimentally (through X-ray and neutron powder diffraction, magnetization, specific heat, dielectric permittivity, and ESR techniques) and theoretically (by means of ab initio density functional theory (DFT) calculations within the spin-polarized generalized gradient approximation). MnSnTeO6 is isostructural with MnSb2O6 (space group P321) and does not show any structural transition between 3 and 300 K. The magnetic susceptibility and specific heat exhibit an antiferromagnetic ordering at TN ≈ 9.8 K, which is confirmed by low-temperature neutron data. At the same time, the thermodynamic parameters demonstrate an additional anomaly on the temperature dependences of magnetic susceptibility χ(T), specific heat Cp(T) and dielectric permittivity ϵ(T) at T∗ ≈ 4.9 K, which is characterized by significant temperature hysteresis. Clear enhancement of the dielectric permittivity at T∗ is most likely to reflect the coupling of dielectric and magnetic subsystems leading to development of electric polarization. It was established that the ground state of MnSnTeO6 is stabilized by seven exchange parameters, and neutron diffraction revealed incommensurate magnetic structure with propagation vector k = (0, 0, 0.183) analogous to that of MnSb2O6. Ab initio DFT calculations demonstrate that the strongest exchange coupling occurs between planes along diagonals. All exchange parameters are antiferromagnetic and reveal moderate frustration. Copyright © 2020 American Chemical Society. The reported study was funded by Russian Science Foundation according to the research project nos. 18-12-00375 (A.K. and M.K.) for neutron studies and 17-12-01207 (E.Z. and S.S.) for magnetic, dielectric and specific heat studies as well as theoretical calculations. Sample preparation and diffraction studies by M.E., M.K., A.K., and V.N. were supported by the grant 18-03-00714 from the Russian Foundation for Basic Research. V.N. thanks the International Centre for Diffraction Data for Grant-in-Aid 00-15. A.V. and S.S. acknowledge the support by the Russian Ministry of Education and Science of the Russian Federation through NUST MISiS grant K2-2017-084 and by the Act 211 of the Government of Russia, contracts 02.A03.21.0004, 02.A03.21.0011, and 02.A03.21.0006. We thank Dr. Yu.V. Popov (SFU’s Shared Use Centre “Research in Mineral Resources and Environment”) for the EDX analysis.

Three caesium-bearing borophosphates, Cs[BP2O6(OH)2] (I), Cs0.51Mn1.17(H2O)2[BP2O8]·0.45H2O (II) and CsMn[BP2O8(OH)] (III), were synthesized by a hydrothermal method at 473–523 K. Their crystal structures have been studied by means of single-crystal X-ray diffraction; all three structures comprise borophosphate chain anions with a B:P ratio of 1:2. The unique construction of (I) is based on four-membered-ring chains running parallel to the [010] direction. These protonated borophosphate chains are linked via hydrogen-bond interactions to form a 3D framework with caesium cations incorporated. (II) is the first Cs and Mn2+,Mn3+member of a known family characterized by [BP2O8]∞helical chains running along [001]. These chains are connected through MnO4(H2O)2octahedra to form a 3D framework. The caesium cations are disordered over two independent positions in the channels, which they occupy together with water molecules. An additional MnO2(H2O)3bipyramid statistically shares a common edge and two corners with three main Mn octahedra to form tetrameric clusters. The topological relation between the chain anionic fragments of (I) and (II) as well as the structural relation between (I) and previously studied boro- and berillophosphates are discussed. Compound (III) presents the first Mn member of theAIMIII[BP2O8(OH)] family and is characterized by a 3D framework built by open-branched borophosphate chains and MnO5semi-octahedra sharing vertices. The measurements of thermodynamic properties,i.e.magnetizationMand specific heatCp, to 2 K and 30 T, provide evidence that (II) orders antiferromagnetically at the Néel temperatureTN= 4.6 K and exhibits a plateau-like feature under the action of an external magnetic field accompanied by a pronounced magnetocaloric effect.

The manganese end member of triplite-triploidite series of compounds, Mn2(PO4)OH, is synthesized by a hydrothermal method. Its crystal structure is refined in the space group P21/c with a = 12.411(1) Å, b = 13.323(1) Å, c = 10.014(1) Å, β = 108.16(1), V = 1573.3 Å3, Z = 8, and R = 0.0375. Evidenced in measurements of magnetization M and specific heat Cp, Mn2(PO4)OH reaches a long range antiferromagnetic order at TN = 4.6 K. As opposed to both triplite Mn2(PO4)F and triploidite-type Co2(PO4)F, the title compound is magnetically frustrated being characterized by the ratio of Curie-Weiss temperature Θ to Néel temperature TN of about 20. The large value of frustration strength Θ/TN stems from the twisted saw tooth chain geometry of corner sharing triangles of Mn polyhedra, which may be isolated within tubular fragments of a triploidite crystal structure. © 2017 The Royal Society of Chemistry. We thank E. V. Guseva for the X-ray spectral analysis of the sample and N. V. Zubkova for her help in the X-ray experiment. This work was supported by the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST "MISiS" project K2-2016-066 and by RFBR projects 15-05-06742, 16-02-00021 and 17-02-00211. The work was supported by Act 211 Government of the Russian Federation, contracts 02.A03.21.0004, 02.A03.21.0006 and 02.A03.21.0011.

The formation of long-range magnetic order at low temperatures was established in francisite—type compounds Cu3La(SeO3)2O2X (X = Br and Cl) through measurements of magnetic susceptibility, magnetization, specific heat and X-band electron spin resonance. The significantly enhanced critical index p = 1.0 ± 0.1 in Cu3La(SeO3)2Br and p = 0.8 ± 0.1 in Cu3La(SeO3)2Cl in the temperature dependence of the width of ESR signal evidence the reduced dimensionality of the kagome-type francisite’s magnetic subsystem. Under action of external magnetic field, the presumably non-collinear six-sublattices antiferromagnetic structure of these compounds experiences the first-order metamagnetic transformation. The B–T magnetic phase diagrams were established from the positions of singularities in temperature and field dependences of thermodynamic properties. Contrary to pristine mineral Cu3Bi(SeO3)2Cl, no signature of structural phase transition was detected.

The manganese orthophosphate, Mn3(PO4)2, is characterized by the rich variety of polymorphous modifications, α-, β'-, and γ-phases, crystallized in monoclinic P21/c (P21/n) space group type with unit cell volume ratios of 2:6:1. The crystal structures of these phases are constituted by three-dimensional framework of corner- and edge-sharing [MnO5] and [MnO6] polyhedra strengthened by [PO4] tetrahedra. All compounds experience long-range antiferromagnetic order at Neel temperature TN = 21.9 K (α-phase), 12.3 K (β'-phase), and 13.3 K (γ-phase). Additionally, second magnetic phase transition takes place at T* = 10.3 K in β'-phase. The magnetization curves of α- and β'-modifications evidence spin-floplike features at B = 1.9 and 3.7 T, while the γ-Mn3(PO4)2 stands out for an extended one-third magnetization plateau stabilized in the range of magnetic field B = 7.5-23.5 T. The first-principles calculations define the main paths of superexchange interaction between Mn spins in these polymorphs. The spin model for α-phase is found to be characterized by collection of uniform and alternating chains, which are coupled in all three directions. The strongest magnetic exchange interaction in γ-phase emphasizes the trimer units, which make chains that are in turn weakly coupled to each other. The spin model of β'-phase turns out to be more complex compared to α- or γ-phase. It shows complex chain structures involving exchange interactions between Mn2 (Mn2', Mn2″) and Mn3 (Mn3', Mn3″). These chains interact through exchanges involving Mn1 (Mn1', Mn1″) spins.