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Magnetization measurements were carried out in the in field-cooled (FC) and in zero-field-cooled (ZFC) conditions versus temperature, T, and external magnetic field, H, on a sigma-phase Fe47Mo53 compound. Analysis of the measured MFC and MZFC curves yielded values of characteristic temperatures: magnetic ordering (Curie) temperature, TC, irreversibility temperature, Tir, temperature of the maximum in MZFC, Tm, identified as the Nėel (TN) temperature, and cross-over temperature, Tco. Based on these temperatures a magnetic phase diagram in the H-T plane was outlined. The field dependences of the characteristic temperatures viz. of the irreversibility and of the cross-over temperatures were described in terms of a power law with the exponent 0.5(1). In the whole range of H i.e. up to 800 Oe, except the one H ≤ 50 Oe, a rare double re-entrant transition viz. PM → FM → AF → SG takes place. For small fields i.e. H ≤ 50 Oe a single re-entrant transition viz. PM → FM → SG is revealed.

The present work is devoted to the magnetic behaviour of Mn12-stearate single-molecule magnets ( [ Mn 12 O 12 ( CH 3 ( CH 2 ) 16 CO 2 ) 11 ( CH 3 CO 2 ) 5 ( H 2 O ) 4 ] · 2 CH 3 COOH ) immobilized inside the SBA-15 mesoporous silica. The stearate’s complexed Mn12, in contrast to the commonly used Mn12-acetate, is soluble in most organic solvents and resistant against water catalyzed reduction. Thus, the precise functionalization of SBA-15 silica by these molecules is possible with no use of sophisticated laboratory equipment. The modified silica matrix in this case provides controlled separation of magnetic molecules, by the use of anchoring units placed inside pores. In order to check the properties of Mn12-stearate molecules regularly distributed inside silica matrix, and check their interactions, samples containing three different concentration of Mn12-stearate molecules were prepared and compared with the bulk Mn12-stearate. All materials have been examined by means of infrared spectroscopy, transmission electron microscopy, X-ray diffraction and squid magnetometry. The obtained results confirmed the successful immobilization of magnetic molecules inside the silica matrices. Moreover, the results of magnetic tests showed a correlation between the amount of magnetic molecules placed inside the mesopores and the magnetic properties of the obtained hybrid materials.

The molecule- based bilayer system composed of hard Ni3.38[Fe(CN)6]2⋅nH2O and soft Ni3.1[Cr(CN)6]2⋅nH2O ferromagnetic Prussian blue analogues has been fabricated on a solid substrate by “layer by layer” deposition. The structure and morphology characterization as well as results of magnetic measurements are described. The thickness of the bilayer is ca. 140 nm including a 35 nm interface. This bilayer system shows anisotropic magnetic properties reflected in the shape of magnetic hysteresis measured in various film orientation with respect to the direction of external magnetic field. There is no exchange interaction between hard and soft magnetic layer and irrespective of bilayer orientation, the magnetization and demagnetization process of both Ni3.38[Fe(CN)6]2⋅nH2O and Ni3.1[Cr(CN)6]2⋅nH2O layers occurs independently.

Invited for the cover of this issue is research led by Magdalena Fitta at the Institute of Nuclear Physics, Krakow, Poland, in collaboration with scientists at the Jagiellonian University, Institute of Metallurgy and Materials Science, and Krakow University of Technology. The cover image shows the temperature dependence of the change in magnetic entropy for a thin film of a Prussian blue analogue at various external magnetic fields.

Low temperature M\"ossbauer spectroscopic and magnetization measurements were performed on a crystalline sample of Fe-gluconate. Fe atoms were revealed to exist in two phases i.e. a major (90-94 pct.) and a minor (6-10 pct.). Based on values of spectral parameters the former can be regarded as ferrous and the latter as ferric. A sub spectrum associated with the ferric phase shows a significant broadening below ca. 30 K corresponding to 7.5 kGs. A magnetic origin of the effect was confirmed by the magnetization measurements. Evidence on the effect of the magnetism on the lattice vibrations of Fe atoms in both components was found. The Debye temperature, T_D, associated with the vibrations of Fe2+ ions is by a factor of about 2 smaller in the temperature range below ca. 30 K than the one determined from the data measured above ca. 30 K. Interestingly, the T_D-value found for the Fe3+ ions from the data recorded below ca.30 K is about two times smaller than the corresponding value determined for the Fe2+ ions., Comment: 19 Pages, 12 Figures, 2 Tables, 17 References

We present a series of remarkable structural transformations for a family of layered metal–organic frameworks (MOFs) in a three-step solid-state reaction cycle. The cycle represents new dynamic behavior of 2D coordination polymers and involves the sequence of reactions: {[Mn2(ina)4(H2O)2]·2EtOH}n (JUK-1) → {(NH4)2[Mn(ina)2(NCS)2]}n·xH2O (JUK-2) → {[Mn2(ina)2(Hina)2(NCS)2]}n (JUK-3) → JUK-1 (Hina = isonicotinic acid), each accompanied by rearrangement of intralayer coordination bonds and each induced by a different external stimulus. In situ investigation of the first step of the cycle by combined synchrotron X-ray diffraction and Raman spectroscopy reveals direct mechanochemical unzipping of JUK-1 bilayers to respective JUK-2 layers with reaction rates dependent on the milling conditions. In contrast, the reverse zipping of JUK-2 layers involves two steps and proceeds through a new MOF (JUK-3) whose structure was elucidated by powder X-ray diffraction. Magnetic measurements confirm conversions of manganese nodes in the reaction cycle. The findings indicate the possibility of developing coordination-based assemblies with large structural responses for use in smart stimuli-responsive systems and sensor technologies.

The structural and magnetic properties of Ni 50 Mn 37.5 Sn 12.5 single crystal were investigated. The alloy undergoes martensitic transformation at 308 K from the austenite phase to the structurally modulated tetragonal 4M martensite phase with lattice parameters a 4M = 6.177 A, c 4M = 5.669 A. The alloy shows 7.9% pre-strain upon uniaxial compression along the 〈001〉 direction, which is near the theoretical 8.2% maximum twinning strain. Magnetization measurements reveal that the magnetic anisotropy of the martensite phase is uniaxial with the easy magnetization axis corresponding to the shortest c axis of the tetragonally distorted unit cell, while its a axis is the hard magnetization direction. The magnetic anisotropy constant K u saturates at low temperature around 7 × 10 4 J/m 3 and then gradually decreases with increasing temperature as the system approaches the Curie temperature of martensite at 215 K.

The SBA-15 silica thin films containing copper ions anchored inside channels via propyl phosphonate groups are investigated. Such materials were prepared in the form of thin films, with hexagonally arranged pores, laying rectilinear to the substrate surface. However, in the case of our thin films, their free standing form allowed for additional research possibilities, that are not obtainable for typical thin films on a substrate. The structural properties of the samples were investigated by X-ray reflectometry, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The molecular structure was examined by Raman spectroscopy supported by numerical simulations. Magnetic measurements (SQUID magnetometry and EPR spectroscopy) showed weak antiferromagnetic interactions between active units inside silica channels. Consequently, the pores arrangement was determined and the process of copper ions anchoring by propyl phosphonate groups was verified in unambiguous way. Moreover, the type of interactions between magnetic atoms was determined.

A study of magnetocaloric effect of a structurally unique molecular magnet built of spin clusters with the pentadecanuclear Ni(II) 9 W(V) 6 core forming a cube-like framework is reported. The compound crystallizes in the triclinic system. The clusters display anisotropy quantified with the axial D =0.07 K and rhombic E =0.023 K anisotropy constants. The temperature dependences of magnetic entropy change Δ S M as well as the adiabatic temperature change Δ T ad due to applied field change μ 0 Δ H ranging from 1 to 9 T have been determined by employing the relaxation calorimetry measurements in applied field. The maximum value of Δ S M for μ 0 Δ H =5 T is 18.38 J K −1 mol −1 (3.36 J K −1 kg −1 ) at 4.3 K. The corresponding maximum value of Δ T ad =4.6 K is attained at 2.2 K. The occurrence of the inverse MCE has been observed at high temperatures for small field change values. The temperature dependence of the exponent n characterizing the field dependence of Δ S M has been estimated and discussed. The study revealed that the compound may be treated as a possible candidate for cryogenic magnetic cooling.

Changes in structure and magnetic properties accompanying guest removal, inclusion, or exchange in two CN-bridged 2D networks of honeycomb topology: {[Ni(cyclam)]3[Fe(CN)6]2}n (1) and {[Ni(cyclam)]3[Cr(CN)6]2}n (2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) were studied by PXRD and magnetic measurements. For each compound four pseudopolymorphic forms differing in structure and magnetic characteristics were identified: fully hydrated form stable in water, partly hydrated form stable in the air at ambient conditions, anhydrous form, and MeOH-modified form. All forms can be reversibly transformed into one another by several interconversion pathways, which fully correspond between Fe and Cr compounds. All forms of 1 and 2 are metamagnetic-like with varied Tc and critical field Hcr. For several forms, differently shaped magnetic hysteresis loops can be observed. For the partly hydrated and MeOH modified forms structure models are proposed on the basis of PXRD data. Correlations between structural features an...

The combined effect of ball milling and subsequent heat treatment on microstructure, magnetic, magnetocaloric and exchange bias properties of Ni48Mn39.5Sn10.5Al2 ribbons is reported. The annealing treatment results in the increase of the critical martensitic transformation temperature. The magnetic entropy change ΔSM of the order of 7.9 and −2.3 J kg K−1 for the annealed 50–32 µm powder fraction is determined. This is less than in the as melt spun ribbon but appears at a considerably higher temperature. At the same time EB is decreased due to annealing treatment. This decrease is attributed to the strengthened ferromagnetic exchange coupling due heat induced stress and structural relaxation.

Octacyanometallate-based compounds displaying a rich pallet of interesting physical and chemical properties, are key materials in the field of molecular magnetism. The [M(CN)8]n− complexes, (M = WV, MoV, NbIV), are universal building blocks as they lead to various spatial structures, depending on the surrounding ligands and the choice of the metal ion. One of the functionalities of the octacyanometallate-based coordination polymers or clusters is the magnetocaloric effect (MCE), consisting in a change of the material temperature upon the application of a magnetic field. In this review, we focus on different approaches to MCE investigation. We present examples of magnetic entropy change ΔSm and adiabatic temperature change ΔTad, determined using calorimetric measurements supplemented with the algebraic extrapolation of the data down to 0 K. At the field change of 5T, the compound built of high spin clusters Ni9[W(CN)8]6 showed a maximum value of −ΔSm equal to 18.38 J·K−1 mol−1 at 4.3 K, while the corresponding maximum ΔTad = 4.6 K was attained at 2.2 K. These values revealed that this molecular material may be treated as a possible candidate for cryogenic magnetic cooling. Values obtained for ferrimagnetic polymers at temperatures close to their magnetic ordering temperatures, Tc, were lower, i.e., −ΔSm = 6.83 J·K−1 mol−1 (ΔTad = 1.42 K) and −ΔSm = 4.9 J·K−1 mol−1 (ΔTad = 2 K) for {[MnII(pyrazole)4]2[NbIV(CN)8]·4H2O}n and{[FeII(pyrazole)4]2[NbIV(CN)8]·4H2O}n, respectively. MCE results have been obtained also for other -[Nb(CN)8]-based manganese polymers, showing significant Tc dependence on pressure or the remarkable magnetic sponge behaviour. Using the data obtained for compounds with different Tc, due to dissimilar ligands or other phase of the material, the ΔSm ~ Tc−2/3 relation stemming from the molecular field theory was confirmed. The characteristic index n in the ΔSm ~ ΔHn dependence, and the critical exponents, related to n, were determined, pointing to the 3D Heisenberg model as the most adequate for the description of these particular compounds. At last, results of the rotating magnetocaloric effect (RMCE), which is a new technique efficient in the case of layered magnetic systems, are presented. Data have been obtained and discussed for single crystals of two 2D molecular magnets: ferrimagnetic {MnII(R-mpm)2]2[NbIV(CN)8]}∙4H2O (mpm = α-methyl-2-pyridinemethanol) and a strongly anisotropic (tetren)Cu4[W(CN)8]4 bilayered magnet showing the topological Berezinskii-Kosterlitz-Thouless transition.

This paper presents the synthesis and investigation of the magnetic properties of mesoporous silica SBA-15 functionalized with Mn12 ([Mn12O12(CH3COO)16(H2O)4]·2CH3COOH·4H2O) high-spin molecular clusters. The SBA-Mn12 sample has been examined by means of X-ray diffraction, infrared spectroscopy, nitrogen sorption and TEM techniques. AC and DC magnetic measurements, including measurements of the magnetocaloric effect (MCE) were carried out both for SBA-Mn12 and for polycrystalline Mn12. An increase in the activation energy and in the distribution of relaxation times was observed for SBA-Mn12 as compared to those of Mn12. Differences in the MCE were also revealed. The maximum magnetic entropy change at the field change of 50 kOe for SBA-Mn12 is equal to 13.8 J K−1 mol−1 at T = 2.8 K, which is significantly less than 25.3 J K−1 mol−1 observed for Mn12 at 3.2 K. The altered relaxation and the magnetocaloric effect point to a successful incorporation of Mn12 molecules into the silica channels.

The paper reports studies of the (1−x)Ba0.95Pb0.05TiO3 – xCo2O3 (x≤0.02) ceramics. Results of X-ray powder diffraction, dielectric, magnetic and IR measurements, as well as ab initio simulations are presented. The Co-doping induces small decrease of the (c/a) tetragonality of the perovskite lattice and leads to the gradual shift of the ferroelectric transition temperature from 398 K for x=0 down to 357 K for x=0.02. The conductivity activation energies are in the range 0.8–0.9 eV in agreement with the calculations. The high-temperature conductivity can be ascribed by the migration of oxygen vacancies introduced to compensate the charge deficiency due to Co3+ valence at the B-site of the perovskite lattice. At the base of present data we can say that BPTC is promising new multiferroic material with weak coupling between magnetic and ferroelectric properties.

In the present work we present mesoporous silica SBA-15 containing propyl-nickel phosphonate study towards confirmation of synthesis procedure correctness. The structure of mesoporous sample was tested by TEM microscopy, N 2 sorption tests and X-ray scattering. To probe bounding between nickel atoms and phosphonic units the Raman spectroscopy was carried out. As a support of Raman scattering, the theoretical calculations were made based on density functional theory, with the B3LYP method. By comparison of the calculated vibrational spectra of the molecule with experimental results, distribution of the active units inside silica matrix has been determined. Magnetic measurements were carried out to find nickel ions concentration inside the mesoporous matrix, and also to determine nickel ions environment. Both magnetic and Raman study confirm the efficiency of the synthesis and corroborate the homogenous distribution of nickel–phosphonate active units in silica matrix.

We have studied the effect of Fe for Mn substitution on magnetic properties of NdMn 1− x Fe x O 3+ δ compounds. Our heat capacity, AC susceptibility and magnetization measurements revealed that the transition from paramagnetic to magnetically ordered state of the Mn sublattice decreases linearly from T N =74.9 K to T N =49 K with doping up to x =0.25. The ordering temperature T 1 of Nd sublattice varies in a non-monotonous way in the temperature range 11–16 K. For x =0.3, the ordering of the Mn/Fe sublattice is residual, while the magnetism in Nd sublattice seems to be intact. The broad maximum in heat capacity C ( T ) at about 10 K was ascribed by 2-level Schottky contribution ( Δ =21(1) K) for x =0, but this description failed for Fe-doped samples. An upturn of C ( T ) at temperatures below 0.5 K was observed on NdMnO 3 and can be accounted to nuclear contribution. A more detailed study of AC susceptibility performed on samples with x =0.1 and 0.2 revealed a shift of both peaks to higher temperature with increasing frequency. The compensation temperature and a large negative field-cooled magnetization was observed for concentrations x =0.2 and x =0.25.

One of the most important challenges of modern science and technology is the quest for novel and tuneable materials, the properties of which can be widely controlled by chemical modifications or external stimuli. Simultaneously, an interest in the development of magnetic thin films also gains significant attention. In the current paper we bring together both these challenges and present a study of a new type of low-dimensional nickel hexacyanoferrate/chromate system. Thin films were obtained by the "layer by layer" deposition technique, where the ratio of Fe/Cr was controlled by the dipping sequence. The scope of this work is a comprehensive analysis of structural, spectroscopic and magnetic properties of the compound and the investigation of the evolution of material properties induced by the change of the chemical composition.

A C14 Nb0.975Fe2.025 Laves phase compound was investigated aimed at determining the H-T magnetic phase diagram. Magnetization, M, and AC magnetic susceptibility measurements were performed. Concerning the former field-cooled and zero-field-cooled M-curves were recorded in the temperature range of 2-200K and in applied magnetic field, H, up to 1000 Oe, isothermal M(H) curves at 2 K, 5 K, 50 K, 80 K and 110 K as well as hysteresis loops at several temperatures over the field range of -10 to +10kOe. Regarding the AC susceptibility, both real and imaginary components were registered as a function of increasing temperature in the interval of 2 K - 150 K at the frequencies of the oscillating field, f, from 3 Hz up to 999 Hz. An influence of the external DC magnetic field, H, on the temperature dependence of the AC susceptibility was investigated, too. The measurements clearly demonstrated that the magnetism of the studied sample is weak, itinerant and has a reentrant character. Based on the obtained results a magnetic phase diagram has been constructed in the H-T coordinates., Comment: 15 pages, 11 figures, 31 references

New [Co(SCN)2(L)4/2] complexes, where L = b-pic (1), pyCH2OH (2), py(CH2)3OH (3), 1,2,4- triazolo[1,5-a]pyrimidine (4), [CoCl2(urotrop)2] (5), and [Co(DMIM)3]Cl2 H2O (6) where urotrop = hexamethylenetetramine and DMIM = 2,20-bis(4,5-dimethylimidazolyl) were synthesized in simple reactions of CoCl2 6H2O with ammonia thiocyanate and pyridine type ligands or urotropine and diimidazolyl ligands with cobalt(II) chloride in methanol solutions. The orthorhombic crystallization for (1), (2), and (4), the monoclinic one for (3) and (5) as well as the hexagonal one for (6) were found. The plots of the overlap population density-of-states indicated nonbonding character of the interactions between pyridine derivatives ligands and cobalt(II) ions in the complexes (1)–(4). The electronic spectra showed almost perfect octahedral complex in the case of (6). The magnetic susceptibility measurements revealed paramagnetic behavior with low values of the Curie–Weiss temperature, positive for complex (5) and negative for the other ones, although the transition to collective magnetic state at low temperatures for (4) and (5) was evidenced by an observation of antiferromagnetic coupling with Ne´el temperature of 4.5 K and the ferromagnetic one with Curie temperature of 10 K, respectively.

[Mn(SCN)2(L)4/2] where L = py, γ-pic, pyCH2OH, py–NH–py (dpa) complexes have been prepared and studied by IR and UV-Vis spectroscopy, and X-ray crystallography. Electronic structures of the complexes were calculated using DFT method, and the descriptions of frontier molecular orbitals and the relocation of the electron density of the compounds were determined. The differences in acceptor properties of the used pyridine derivatives ligands were shown in the values of ligand field parameters determined from electronic spectra of the complexes. The magnetic properties revealed paramagnetic behavior with a weak ferromagnetic interaction and the van Vleck contribution for [Mn(SCN)2(py)4] (1), ideal paramagnetism for [Mn(SCN)2(γ-pic)4] (2) and a weak antiferromagnetic interaction and diamagnetic contribution for [Mn(SCN)2(pyCH2OH)2] (3).

New [Ni(SCN)2(L)4/2] complexes, where L = py (1), γ-pic (2), pyCH2OH (3), py(CH2)3OH (4) were synthesized in simple reactions of NiCl2·6H2O with ammonia thiocyanate and pyridine type ligands in methanol solutions. Blue crystals of [Ni(SCN)2(py)4] (1), [Ni(SCN)2(pyCH2OH)2] (3) and [Ni(SCN)2(py(CH2)3OH)2] (4) crystallize in the monoclinic system, blue crystal of [Ni(SCN)2(γ-pic)4] (2) – in the tetragonal one, and red crystal of [Ni(SCN)2(PPh3)2] (5) – in the triclinic one. The ligands of complexes (1) and (3) were indicated as rather strong π-acceptors while that of complex (4) one has some π-donor properties. When the aliphatic chain (CH2) elongates in the sequence: (1), (3) and (4), an increase in the orbital contribution to the magnetic moment and a decrease in the 10Dq value of the d orbital splitting are related to the change of the point group symmetry from D2h, via D2v to C2h.

Pentadecanuclear cyano-bridged high spin {MnII9WV6(CN)48(solv)24} clusters serve as bifunctional molecular building blocks in the construction of a {MnII9[WV(CN)8]6(dpe)5(MeOH)10}·14MeOH (dpe = trans-1,2-di(4-pyridyl)ethylene) organic−inorganic hybrid network of I1O2 topology. The intercluster connections are formed by Mn−NC−W and Mn−dpe−Mn linkages. The Mn−NC−W linkages lead to one-dimensional (1D) cyanido-bridged nanowires {Mn9W6}n with a van der Vaals diameter changing periodically from ∼1 to ∼1.5 A, with Mn−dpe−Mn linkages controlling the effective distances between them. The magnetic measurements suggest the superparamagnetic behavior of {Mn9W6}n skeletons below 100 K due to the internal ferrimagnetic ordering through CN− bridges. Below 3.5 K, weak antiferromagnetic interactions between the {Mn9W6}n operate, with two inflection points H1 = 100 Oe and H2 = 480 Oe observed in the M(H) curve at 1.8 K.

Physical properties of TbCu2X2 (X = Si, Ge) and HoCu2Si2, crystallizing with the tetragonal ThCr2Si2-type crystal structure, were investigated by means of neutron diffraction as well as by magnetic and calorimetric measurements. All compounds exhibit antiferromagnetic ordering below TN equal to 12 K for TbCu2Si2, 13 K for TbCu2Ge2 and 6.4 K for HoCu2Si2. Neutron diffraction data indicate collinear antiferromagnetic structure described by the propagation vector k → = [ ( 1 / 2 ) , 0 , ( 1 / 2 ) ] at low temperatures. While increasing temperature the direction of the Tb magnetic moment changes from [1 1 0] to [0 1 0] at Tt = 8.5 K for TbCu2Si2 and 9.7 K for TbCu2Ge2. In HoCu2Si2 a change of the magnetic structure from the collinear to a modulated one described by the propagation vector k → = [ k x , 0 , k z ] was found at Tt = 4.7 K.

Magnetization and phase sensitive AC susceptibility was measured for the annealed and as-cast samples of ferromagnetic UCu2Ge2, T C = 107 K . Special attention was paid to the low temperature range, T 50 K , which is interesting due to the magnetization decrease and frozen AC response. The hysteresis loops showed a remanence of ≈87% and a fast, thermally activated decrease in the coercivity field. Thermoremanent magnetization at 4.3 K decayed with the relaxation time ≈1∗103 s. The strong increase of the χ A C with the amplitude of the driving field was observed. All these results point to a very large anisotropy of the compound at the lowest temperatures. Phase transition to the randomly canted ferromagnetic phase at T ≈ 55 K was detected in the measurement of the third order non-linear susceptibility. It is concluded that the origin of the transition is the strong temperature dependence of magnetic anisotropy.

Carbon coated cobalt-, nickeland iron-nanoparticles were prepared by chemical method and their structural and magnetic properties were investigated. The samples were synthesized by carburization of the nanocrystalline form of the appropriate metal in CH4, followed up by the reduction of the obtained carbon deposits. The X-ray diffraction and transmission electron microscopy study revealed carbon coated Co-, Niand Fe-nanocapsules of the mean size ca. 50 nm, and a small amount of carbon nanotubes. The measurements of magnetization and AC susceptibility were carried out for samples with different carbon content. A special attention was paid to the low temperature magnetic behavior. Decrease in the saturation moment at T = 4.2 K due to the nanosize of the particles was stronger for the samples with higher carbon content, while the coercivity field (610 Oe, 330 Oe and 390 Oe, for Co-, Ni-, and Fe-particles, respectively) was independent of carbon content. From the temperature dependence of AC and DC susceptibility a wide size distribution of the particles and blocking temperature above room temperature could be expected.

Polycrystalline samples of TbNi1ixAuxIn for x = 0:1, 0.2, 0.4, 0.6 and 0.8 were prepared and studied by powder X-ray and neutron difiraction and ac magnetic susceptibility measurements. These compounds crystallize in the hexagonal ZrNiAl-type structure. With increasing Au content a change in the magnetic structure is observed. For x = 0:1, 0.2 and 0.4 the magnetic order is described by the propagation vector k = (1/2, 0, 1/2)

A novel 3D cyano-bridged hybrid ferrimagnet { Mn 2 II ( imH ) 2 ( H 2 O ) 4 [ Nb IV ( CN ) 8 ] } · 4 H 2 O 1 (imH = imidazole) of T c = 25 K is reported. Its 3D inorganic –Nb–CN–Mn– framework is built of two groups of mutually parallel 1D-ladders cross-linked at niobium centers. Imidazole molecules reveal terminal coordination mode only. We discuss structural features in the context of 3D –Nb–CN–Mn– framework of 1 , comparing it with that of { Mn 2 II ( pzdo ) ( H 2 O ) 4 [ Nb IV ( CN ) 8 ] } · 5 H 2 O 2 ferrimagnet with T c = 37 K reported by us [Inorg. Chem. 46 (2007) 10416]. The differences in T c are explained in respect to the metric parameters and positions of bridging linkages at [Nb(CN) 8 ] 4− polyhedra. Comparison of infrared spectra of 1 and free imH is also provided.

Magnetic properties of a sigma-phase Fe60V40 intermetallic compound were studied by means of ac and dc magnetic susceptibility and magnetocaloric effect measurements. The compound is a soft magnet yet it was found to behave like a re-entrant spin-glass system. The magnetic ordering temperature was found to be T_C ca.170 K, while the spin-freezing temperature was ca.164 K. Its relative shift per decade of ac frequency was 0.002, a value smaller than that typical of canonical spin-glasses. Magnetic entropy change, DeltaS, in the vicinity of T_C was determined for magnetic field, H, ranging between 5 and 50 kOe. Analysis of DeltaS in terms of the power law yielded the critical exponent, n, vs. temperature with the minimum value of 0.75 at T_C, while from the analysis of a relative shift of the maximum value of DeltaS with the field a critical exponent Delta=1.7 was obtained. Based on scaling laws relationships values of other two exponents viz. betha=0.6 and gamma=1 were determined., Comment: 12 pages, 18 figures, 24 references

Quantum chemical calculations are employed to elucidate the origin of a puzzling diamagnetism for a hexacyanomolybdate(IV) anion, [Mo(CN)6](2-), which was previously reported by Szklarzewicz et al. [Inorg. Chem., 2007, 46, 9531-9533]. The diamagnetism is surprising because for the octahedral (d)(2) complex one would rather expect a (paramagnetic) triplet ground state, clearly favored over a (diamagnetic) singlet state by an exchange interaction between two d electrons in the t2g orbitals. Nevertheless, the present calculations reveal that the minimum energy structure of isolated [Mo(CN)6](2-) is not an octahedron, but a trigonal prism; the latter geometry allows maximization of a σ-donation from the cyanides to the electron-deficient Mo(iv) center. Unlike for the octahedron, for the trigonal prism structure the singlet and triplet spin states are close in energy to within a few kcal mol(-1). Although the actual relative energy of the two spin states turns out to be method-dependent, the complete active space calculations (CASPT2; with the appropriate choice of the IPEA shift parameter) can reproduce the singlet ground state, in agreement with the experimentally observed diamagnetism. Moreover, magnetic measurements reveal a slight increase of the magnetic susceptibility with the increase of temperature from 100 to 300 K, suggesting an admixture of a thermally induced paramagnetism (possibly due to Boltzmann population of the low-energy triplet state) on top of the dominant diamagnetism. Our prediction that the geometry of [Mo(CN)6](2-) should significantly deviate from the ideal octahedron, not only in the gas phase, but also in a periodic DFT model of the crystalline phase, as well as the experimentally confirmed diamagnetic properties, does not agree with the previously reported ideal octahedral structure. We suggest that this crystal structure might have been determined incorrectly (e.g., due to overlooked merohedral twinning or superstructure properties) and it should be re-investigated.

Magnetization, magnetic susceptibility, electrical resistivity, thermoelectric power, neutron diffraction and X-Ray photoemission spectroscopy measurements were performed on polycrystalline samples of PrAg 2 Ge 2 and NdAg 2 Ge 2 , both crystallizing with a tetragonal structure of the ThCr 2 Si 2 -type. The data indicate that both compounds order magnetically at low temperatures, PrAg 2 Ge 2 at 12 K and NdAg 2 Ge 2 at 2 K. Neutron diffraction data for the latter indicate antiferromagnetic collinear structure described by the propagation vector k =(½, 0, ½) at 1.5 K. Both compounds exhibit metallic-like electrical behavior. The X-Ray photoemission data indicate that the valence bands are formed mainly by the Ag 4d bands. The spin-orbit splitting values determined from the XPS spectra of Pr and Nd, 3d 5/2 and 3d 3/2 , equal 20.5 eV for the Pr compound and 22.7 eV for the Nd compound. The analysis of these spectra performed on the basis of the Gunnarsson-Schonhammer model indicates a weak hybridization of the 4f electrons with the conduction band.

Magnetic properties of frustrated antiferromagnet TbAuIn are investigated by AC susceptibility, resistivity as well as specific heat measurements. In temperature dependence of the susceptibility two anomalies are visible, one at 33 K and another at 48 K. According to neutron diffraction studies the Neel temperature is 35 K. The second anomaly in the AC susceptibility seems to be attributed to antiferromagnetic cluster-glass state of Tb magnetic moments. The resistivity measurements confirm that TbAuIn exhibits long-range magnetic order below 35 K, moreover they reveal an anomalous behaviour above that temperature. However in the temperature dependence of the specific heat only one anomaly at 30 K is visible. The low temperature behaviour of susceptibility, resistivity and specific heat of the investigated antiferromagnetic material can be described, with a good accuracy, within the spin-wave theory with linear dispersion relation.

New neutron diffraction and ac magnetic susceptibility data concerning phase transitions and magnetic structures of PrCu2Ge2 and NdFe2Ge2 are presented here. In the case of PrCu2Ge2 at low temperatures collinear antiferromagnetic ordering of the AFI type is observed. In the temperature range between Tt = 5.5 K and TN = 15.0 K the collinear and a sine wave modulated structure coexist. The latter phase is a long period modulation along the a-axis described by the propagation vector k = (0.0336(5),0,0). In the case of NdFe2Ge2 the situation is similar: a collinear AFII-type low temperature phase (k = (0,0,1/2)) changes into a non-collinear one (k = (0,0,0.46(1))) at about 12 K. In both compounds in all phases magnetic moments localized on rare earth ions are parallel to the c-axes.

Systematic studies of AC susceptibility in a stoichiometric magnetite single crystal, in a series of low zinc doped magnetite (xZn < 0.04) and in nonstoichiometric magnetite samples (both single crystals and pellets) in the temperature range 4–300 K are presented. Measurements were performed in several AC fields ( $H_{AC}=0.2{-}20\ $ Oe) and at different frequencies (15–6000 Hz). It is suggested that the signal is primarily due to magnetic domain wall movement, strongly influenced by structural domains (twins). Two sets of anomalies were found: the first is associated with the Verwey transition and the second involves two different effects, one at 28 K, observed only in stoichiometric magnetite, and the other at 50 K. While the temperature position of the first anomaly (28 K) does not depend on frequency, the effect at 50 K is associated with an activation process, shifting to higher temperatures with increasing frequency. This last effect may be linked to the low temperature magnetoelectric effects terminating approximately at those temperatures. Qualitatively similar results have been observed by the Magnetic After Effect technique presented in the literature, that is associated with relaxation times that are 104 higher than those characteristic of our technique.

Results of AC susceptibility and DC magnetization measurements for polycrystalline samples of RPd2Ge (R=Tb, Dy, Ho and Er) are presented. All the compounds crystallize in the orthorhombic Fe3C-type structure (space group is Pnma) and are antiferromagnets with the Neel temperature of 21 K for Tb, 16 K for Dy, 6.5 K for Ho and 3 K for Er, respectively. Moreover, below TN, at temperatures Tt roughly equal to TN/2, the data give the evidence for additional phase transitions to another antiferromagnetic state. The characteristic feature of the low-temperature phase is large anisotropy, while for high-temperature phase the anisotropy is smaller and a possibility of the weak uncompensation of the magnetic moments appears. Isothermal magnetization curves for TbPd2Ge and DyPd2Ge show a metamagnetic behaviour with the threshold field and the field-induced hysteresis decreasing with temperature. Irreversibility in the ZFC–FC magnetization temperature runs and the weak frequency dependence of the AC susceptibility are not connected with the spin-glass-like character of the investigated samples. Conclusions of the study are compared with the results of the magnetic neutron diffraction recently published.

The self-assembly of [M(CN) 8 ] 3− (M=Mo, W) anion and polyamine complexes of Cu II [Cu(tetren)] 2+ and [Cu(dien)(H 2 O) 2 ] 2+ (tetren=tetraethylenepentamine, dien=diethylenetriamine) in acidic aqueous solution gives (tetrenH 5 ) 0.8 {Cu II 4 [W V (CN) 8 ] 4 }·7.2H 2 O 1 , (tetrenH 5 ) 0.8 {Cu II 4 [Mo V (CN) 8 ] 4 }·7.2H 2 O 2 , (dienH 3 ){Cu II 3 [W V (CN) 8 ] 3 }·4H 2 O 3 and (dienH 3 ){Cu II 3 [Mo V (CN) 8 ] 3 }·4H 2 O 4 2D coordination polymers. All compounds are structure-related: the crystal structures of isomorphous 1 – 2 and 3 – 4 , respectively, consist of double-layered cyano-bridged {Cu II [W V (CN) 8 ] − } n square grid backbones and non-coordinated fully protonated polyamine countercations as well as H 2 O molecules located between the sheets. The magnetic measurements reveal long range ferromagnetic ordering with sharp phase transitions at T C in range 28–37 K and coercivity in range 30–225 Oe at liquid helium temperature, T =4.3 K.

The magnetic ordering of TbRhSn, crystallizing in the hexagonal ZrNiAl-type structure, has been investigated by high-resolution neutron diffractometry in the temperature range between 1.7 and 23.9 K. Tb in TbRhSn has been found to order magnetically below 19 K. Its magnetic structure corresponds to propagation vector ~ ¼½ 1 ; 0; 1 � ; and by a new group-theoretical analysis is shown to be based on the two irreducible representations t2 and t4: This model also explains the change of magnetic ordering at Tt ¼ 11 K: New aspects of bulk magnetic measurements are also reported. Moreover, our results are compared with previously published data. r 2003 Elsevier Science B.V. All rights reserved.

A sigma-phase Fe65.9V34.1 alloy was investigated with the AC magnetic susceptibility as a function of temperature, frequency and external magnetic field. An evidence was found that its magnetism shows features characteristic of a reentrant behavior viz. two transitions: first at TC ca.312K from the paramagnetic state into the collinear ferromagnetic one, and second at Tf ca.302K to a mixed state (sometimes termed as a ferromagnetic re-entrant spin glass) which, finally, at a lower temperature (TRSG ca.60K) transforms to a state where replica symmetry is broken. The frequency dependence of Tf is lower than that of canonical spin glasses, a feature, that in the light of a high concentration of magnetic carriers, can be understood in terms of a weak coupling between magnetic clusters., Comment: 11 pages, 7 figures, 25 references

A comprehensive study of magnetocaloric effect (MCE) and critical behavior in the {Mn 2 (imH) 2 (H 2 O) 4 [Nb(CN) 8 ]·4H 2 O} n molecular magnet is reported. The compound is an example of a magnetic sponge, where structural changes provoked by dehydration process lead to the increase of T c critical temperature from 25 K for the as-synthesized sample ( 1 ) up to 60 K for the anhydrous one ( 2 ). MCE and critical behavior were investigated by magnetization measurements. The maximum value of magnetic entropy change Δ S , determined by the magnetization measurements for 1 is 6.70 J mol −1 K −1 (8.95 J kg −1 K −1 ) at µ 0 Δ H =5 T, while for 2 it is equal to 4.02 J mol −1 K −1 (7.73 J kg −1 K −1 ) at the same magnetic field change. The field dependence of MCE at T c for 1 and 2 was consistent with critical exponents, which allowed to classify both phases to 3D Heisenberg universality class. The T c - 2 / 3 dependence of the maximum entropy change has been tested using data of 1 and 2 together with MCE data previously reported for other members of the ferrimagnetic Mn 2 - l -[Nb(CN) 8 ] (L=imidazole, pyridazine and pyrazole) series. Experimental MCE results have been compared with the spin contribution to the magnetic entropy change estimated using a molecular field approximation.

AC magnetic susceptibility measurements were performed for ceramics of the Ho1−xPrxBa2Cu3O7−δ system as a function of temperature, frequency, field amplitude and static magnetic field. From the measurements, temperature dependences of intergranular critical currents and corresponding pinning energies at grain boundaries were determined for different Pr concentrations. These critical currents strongly decrease with Pr doping. They are limited by superconductor–insulator–superconductor or superconductor–normal metal–superconductor junctions and for higher Pr concentrations additionally suppressed by flux creep. Also intragranular critical current at 4.3 K was determined as a function of Pr concentration from magnetic hysteresis loops. It is a monotonically decreasing function of Pr doping.

The paper presents two large-scale observations of magnetic treatment of industrial water, aimed at investigating changes in the formation of deposits. First, a four-month experiment is described with two identical 25 kW heat exchangers, where in one case the inlet water was treated by a magneto-hydrodynamic method. Deposits recovered from both exchangers were analyzed chemically, by X-ray diraction, infrared spectroscopy and PIXE. The amount of deposit for untreated water, composed mostly of calcite, increased exponentially with temperature reaching 20 g/m of tube at the warm end of the heat exchanger. The mass of the deposit for magnetically treated water did not depend on temperature and was only ca. 0.5 g/m of tube. It was composed of mainly noncrystalline silica-rich material. Further results were obtained from the practical installation at three blocks of a 1 GW power plant. The soft, amorphous deposit for magnetically treated water had a specic surface area of 80 m 2 /g and an infrared spectrum similar to that of a silicate hydrogel. Therefore, it appeared that, as a result of the passage through the magnetic device, crystallization of carbonates in water was blocked due to initiation of another, competitive process. This process is the activation of the colloidal silica, which will adsorb calcium, magnesium or other metal ions and then precipitate from the solution as the coagulated agglomerate. The most probable mechanism responsible for silica activation is a Lorentz-force induced deformation of the diuse layer leading to the increased counterion concentration in the adsorption layer of the negatively charged silica. PACS. 85.70.-w Magnetic devices { 82.70.Dd Colloids { 33.20.Ea Infrared spectra

The changes in crystallographic, magnetic, and transport properties with calcium substitution in deoxygenated R1−xCaxBa2Cu3O6.1 (R=Y, Eu) system have been investigated. The superconductivity is induced at a calcium content of x=0.26–0.3. However, the induced superconductivity exhibits a low critical field. The system R1−xCaxBa2Cu3O6.1 undergoes an insulator to metal transition. The increase in the effective magnetic moment with Ca substitution is detected. The crystal structure undergoes slight modifications. Although, the observed variation of crystal structure forced by Ca doping does not reproduce the structure modifications characteristic of oxygen doping. The discussed changes in properties of R1−xCaxBa2Cu3O6.1 should be mainly related to hole doping, observed as an increase in formal copper valence, which was confirmed by iodometric titration.

We have investigated Mn(III)–porphyrin–TCNE complexes showing peculiar magnetic properties at low temperatures. The tetraphenylporphyrin ligand is substituted on the periphery of the phenyl rings with different groups. Static and dynamic susceptibility measurements have been carried out on the samples.

Neutron diffraction and magnetic measurements reveal a phase transition in TbCo2Si2 and DyCo2Si2 from a collinear antiferromagnetic AFI type order with the k-vector [001] to an incommensurate sine-modulated magnetic structure described by the wavevector k = (0,0,1-kz). The transition above occurs directly below the N?el temperature and kz is equal to 0.042(1) for TbCo2Si2 and 0.049(1) for DyCo2Si2. In both phases magnetic moments localized on rare earth ions are parallel to the c-axis.

The paper deals with certain charge transfer molecular magnets built of chains with [MnTPP] cations bound to [TCNE] anions (TPP=tetraphenylporphyrin, TCNE=tetracyanoethylene). Magnetic moments, coming from Mn III d orbitals and from anion p orbitals, are strongly coupled in the chain. Three modifications, [MnR 4 TPP][TCNE]×solvent with R (=OC 12 H 25 , F, CN) groups substituted at the periphery of the porphyrin disc, are investigated by means of AC susceptibility and DC magnetization measurements. The temperature T c , of the transition from the short-range one-dimensional ferrimagnetic order to the cooperative low-temperature state, is equal to 22, 27 and 20 K for R=OC 12 H 25 , F and CN, respectively. For the first compound the transition is especially sharp. Below T c , the compounds show both ferromagnetic (FM) and spin-glass (SG) properties, the latter ones caused by random anisotropy due to the solvent. Competition between FM and SG ordering results in “reentrance” to the SG state at the glass temperature T g . At T =4.2 K, compounds with R=OC 12 H 25 and R=F show substantial coercivity and remanant magnetization. For the first sample, the magnetization jump at the virgin curve, identified as the spin flop, is seen at H j ≅ 4 kOe for 4.2 K. The magnetization process changes dramatically with temperature.

The results of the ac susceptibility and dc magnetization in the wide range of temperatures are presented for KCo[Fe(CN)6]·xH2O. Magnetic ordering was revealed at T = 13.2 K. Frequency dependence of the complex susceptibility and non-linear response suggest glassy like behavior.