A new type of antiferrodistortive structure in a double perovskite with Pb

We have found a new structural transition in Pb(2)MnReO(6) at 410 K. Above this temperature, Pb(2)MnReO(6) is cubic with disordered and dynamic atomic displacements manifested in the large thermal parameters of Pb and O atoms. Below 410 K, the antiferrodistortive shift of 2/3 of Pb(2+) cations away from the high-symmetry cubic site produces a new type of monoclinic cell. The unit cell expands at the transition and the heat capacity shows a peak with thermal hysteresis. These features agree with a first order transition. The entropy content of the transition is quite low indicating that the structural disorder has not been completely removed in the low temperature phase. The monoclinic phase of Pb(2)MnReO(6) shows thermally activated conductivity which does not vary when an external magnetic field is applied. A change in the slope of the resistivity curve, observed at the structural phase transition temperature, is related to a slight difference in the activation energy between both phases. It suggests that the condensation of the distortions likely affects the conduction mechanism. The isothermal magnetization measurements reveal the presence of ferromagnetic contributions below 85 K. The ac magnetic susceptibility shows a dynamic peak at 50 K and, in addition, zero-field-cooled and field-cooled magnetization curves diverge strongly below 80 K. These features might be signature of magnetic inhomogeneity. Magnetic loops, obtained at 5 K, do not show saturation in fields up to 9 T. Furthermore, the measured coercivity increases sharply at low temperature indicating an abrupt change in the magnetic anisotropy. We show that all these magnetic properties point out to a ferrimagnetic ordering of Mn and Re atoms in an intermediate valence state.     

Highly porous Co(II)-salicylate metal-organic framework: synthesis, characterization and magnetic properties

A new porous Co(II)-salicylate metal-organic framework material has been synthesized hydrothermally through the reaction of Co(II) chloride with sodium salicylate under mild alkaline pH conditions. To get an idea about the structural aspect of the material from the powder X-ray diffraction (PXRD) pattern, MAUD program has been successfully utilized and the assigned peaks match very well with a new tetragonal phase (space group, P4mm) having the unit cell parameters: a = b = 12.957 (0.042) ?; c = 12.738 (0.019) ?; α = β = γ = 90°, V = 2138.73 ?(3). N(2) adsorption/desorption analyses suggested the material is highly porous in nature having high BET surface area and pore dimensions of 2.0-3.0 nm, which is within the range of small mesopores. Thermogravimetric analysis (TGA) revealed that the H(2)O molecules may be removed from the framework without collapsing the structure and the material is stable up to ca. 573 K. The material is characterized thoroughly by using different characterization tools such as TEM, SEM, UV-visible reflectance spectroscopy, FT IR spectroscopy and photoluminescence spectroscopy. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the cobalt atom and presence of other elements within the framework. The material shows interesting magnetic properties, where the magnetic moments monotonically increase with the decrease in temperature down to 9 K. Below 9 K there is a steep increase in magnetization on further lowering the temperature, thereby suggesting the onset of a long range ferromagnetic transition with ferromagnetic Curie temperature, T(C) = 8.5 K. Furthermore, the M-H curve at 2 K shows a clear hysteresis loop with a coercive field 150 Oe and remnant magnetization 0.8 μ(B)/f.u.     

Combining azide, carboxylate, and 2-pyridyloximate ligands in transition-metal chemistry: ferromagnetic Ni(II)5 clusters with a bowtie skeleton

The combined use of the anion of phenyl(2-pyridyl)ketone oxime (ppko(-)) and azides (N(3)(-)) in nickel(II) carboxylate chemistry has afforded two new Ni(II)(5) clusters, [Ni(5)(O(2)CR')(2)(N(3))(4)(ppko)(4)(MeOH)(4)] [R' = H (1), Me (2)]. The structurally unprecedented {Ni(5)(μ-N(3))(2)(μ(3)-N(3))(2)}(6+) cores of the two clusters are almost identical and contain the five Ni(II) atoms in a bowtie topology. Two N(3)(-) ions are end-on doubly bridging and the other two ions end-on triply bridging. The end-on μ(3)-N(3)(-) groups link the central Ni(II) atoms with the two peripheral metal ions on either side of the molecule, while the Ni···Ni bases of the triangles are each bridged by one end-on μ-N(3)(-) group. Variable-temperature, solid-state direct- (dc) and alternating-current (ac) magnetic susceptibility, and magnetization studies at 2.0 K were carried out on both complexes. The data indicate an overall ferromagnetic behavior and an S = 5 ground state for both compounds. The ac susceptibility studies on 1 reveal nonzero, frequency-dependent out-of-phase (χ(M)") signals at temperatures below ~3.5 K; complex 2 reveals no χ(M)" signals. However, single-crystal magnetization versus dc field scans at variable temperatures and variable sweep rates down to 0.04 K on 1 reveal no noticeable hysteresis loops, except very minor ones at 0.04 K assignable to weak intermolecular interactions propagated by nonclassical hydrogen bonds.     

Solution synthesis of gadolinium nanoparticles

Gadolinium nanoparticles have been produced at subambient temperature by alkalide reduction. The nanoparticles display maxima in the temperature dependence of their magnetization, cooled in the absence of an applied external field, at T(max) of 5.0 and 17.5 K for unheated samples and samples annealed at 1000 degrees C for 4 h, respectively. Field cooled behavior deviates at temperatures slightly above T(max), increasing at lower temperature. Curie-Weiss law fits of the high-temperature data yield magnetic moments in close agreement with those expected for noninteracting Gd(3+) ions, suggesting that the behavior seen is due to a magnetic transition rather than superparamagnetism. Magnetization is linearly dependent on field at temperatures higher than 7-8 times T(max) and shows remanence-free hysteresis at lower temperature, suggesting metamagnetism. Some annealed samples show evidence of additional ferromagnetic interactions below approximately 170 K. Magnetic entropy curves generated from magnetization data are consistent with that expected for a paramagnet.     

Magnetic behavior of USe at low temperatures

The magnetization versus temperature behavior of USe has been investigated in the temperature range from 2.8 to 300°K and in various applied fields up to 21 kOe. A sharp decrease in magnetization is found at low temperatures. This behavior seems to be associated with the rhombohedral distortion in crystal structure, giving rise to a high anisotropy field, below the Curie temperature. Large magnetic hysteresis effects at low temperatures confirm these arguments.     

Monolayer,bilayer, multilayers: evolving magnetic behavior in Langmuir-Blodgett films containing a two-dimensional iron-nickel cyanide square grid network

The assembly of two-dimensional cyanide-bridged Fe(III)-Ni(II) square grid networks at the air-water interface and subsequent transfer of these networks as isolated monolayer, isolated bilayer, and multiple bilayer (multilayer) films via the Langmuir-Blodgett technique results in novel low-dimensional systems in which the effects of dimensionality on magnetic behavior in molecule-based materials can be observed. The magnetic response of these films between 2 < T < 300 K in dc fields from -50 < H < 50 kG and in 4 G ac fields from 1 Hz to 1 kHz are reported. The results show the presence of ferromagnetic domains with characteristic hysteresis in each of the three systems. The magnetic response for all three samples is anisotropic with a stronger field-cooled magnetization observed when the planes of the films are aligned parallel to the applied field. Additionally, each of the three samples shows frequency dependence in both the real and imaginary components of the ac susceptibility. This behavior is interpreted as being characteristic of spin glass-type ordering of ferromagnetic domains to form a cluster glass. A lower glass temperature (T(g)) is observed in the isolated monolayer film relative to the bilayer and multilayer samples. The bilayer sample shows two glass transitions at T(g1) = 3.8 K and T(g2) = 5.4 K, whereas only one transition at T(g) = 5.4 K is observed in the multilayer sample. The different magnetic responses of the three films are attributed to different in-plane, interplane, and long-range dipolar exchange interactions.     

Construction of hydrogen-bonded and coordination-bonded networks of cobalt(II) with pyromellitate: synthesis,structures, and magnetic properties

Synthesis (hydrothermal and metathesis), characterization (UV-vis, IR, TG/DTA), single-crystal X-ray structures, and magnetic properties of three cobalt(II)-pyromellitate complexes, purple [Co(2)(pm)](n) (1), red [Co(2)(pm)(H(2)O)(4)](n) x 2nH(2)O (2), and pink [Co(H(2)O)(6)](H(2)pm) (3) (H(4)pm = pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid)), are described. 1 consists of one-dimensional chains of edge-sharing CoO(6) octahedra that are connected into layers via O-C-O bridges. The layers are held together by the pyromellitate (pm(4-)) backbone to give a three-dimensional structure, each ligand participating in an unprecedented 12 coordination bonds (Co-O) to 10 cobalt atoms. 2 consists of a three-dimensional coordination network possessing cavities in which unbound water molecules reside. This highly symmetric network comprises eight coordinate bonds (Co-O) between oxygen atoms of pm(4-) to six trans-Co(H(2)O)(2). 3 possesses a hydrogen-bonded sandwich structure associating layers of [Co(H(2)O)(6)](2+) and planar H(2)pm(2-). The IR spectra, reflecting the different coordination modes and charges of the pyromellitate, are presented and discussed. The magnetic properties of 1 indicate complex behavior with three ground states (collinear and canted antiferromagnetism and field-induced ferromagnetism). Above the Néel temperature (T(N)) of 16 K it displays paramagnetism with short-range ferromagnetic interactions (Theta = +16.4 K, mu(eff) = 4.90 mu(B) per Co). Below T(N) a weak spontaneous magnetization is observed at 12.8 K in low applied fields (H < 100 Oe). At higher fields (H > 1000 Oe) metamagnetic behavior is observed. Two types of hysteresis loops are observed; one centered about zero field and the second about the metamagnetic critical field. The critical field and the hysteresis width increase as the temperature is lowered. The heat capacity data suggest that 1 has a 2D or 3D magnetic lattice, and the derived magnetic entropy data confirm an anisotropic s(eff) = 1/2 for the cobalt(II) ion. Magnetic susceptibility data indicate that 2 and 3 are paramagnets.     

Cr[(H3N-(CH2)2-PO3)(Cl)(H2O)]: X-ray single-crystal structure and magnetism of a polar organic-inorganic hybrid chromium(II) organophosphonate

Cr[(H(3)N-(CH(2))(2)-PO(3))(Cl)(H(2)O)], a rare example of a polar organic-inorganic hybrid material containing Cr(2+), was prepared from CrCl(2), 2-aminoethylphosphonic acid, and urea in water and isolated as light-blue crystals. It crystallizes in the noncentrosymmetric monoclinic space group P2(1), with a = 5.249(1) A, b = 14.133(3) A, c = 5.275(1) A, and beta = 105.55(2) degrees. The inorganic layer of the hybrid network is formed by Cr(II) five-coordinated by three oxygen atoms from the phosphonates and one from the water molecule in a square pyramidal unit, whose apical position is occupied by the Cl(-) ion. Hydrogen bonds are established between the coordinating water molecule and the oxygen atoms of adjacent phosphonate ligands. The inorganic network is interspersed by ethylammonium groups, and the terminal ammonium moiety is linked to the apical Cl(-) ions through hydrogen bonds. Electrostatic interactions as well as hydrogen bonds and the coordinated chlorine atoms ensure the cohesion of the 3D structure. The lattice is polar (lack of inversion center), and this fact determines the magnetic behavior of the compound at low temperatures. The magnetic susceptibility data in the temperature range from 300 to 50 K show Curie-Weiss behavior, with C = 2.716 cm(3) K mol(-1) and the Weiss constant theta = -2.2 K. The corresponding effective magnetic moment of 4.7 mu(B) compares well with the expected value for Cr(2+) in d(4) high-spin configuration. A slight decrease of the chiT product versus T observed at temperatures below 50 K indicates nearest-neighbor antiferromagnetic exchange interactions. On cooling below T = 6 K, the magnetic susceptibility increases sharply up to a maximum at ca. 5 K and then decreases again. Below T = 6 K, hysteresis loops taken at different temperatures show that Cr[(H(3)N-(CH(2))(2)-PO(3))(Cl)(H(2)O)] behaves as a weak ferromagnet with the critical temperature T(N) at 5.5 K. The spin canting is responsible of the long-range magnetic ordering. The values of the coercive field, H(c), and of remnant magnetization, M(r), obtained from the hysteresis loop at T = 4.5 K (the lowest measured temperature) are 30 Oe and 0.08 mu(B), respectively.     

Canted antiferromagnetism and spin reorientation transition in layered inorganic-organic perovskite (C6H5CH2CH2NH3)2MnCl4

This work presents the synthesis, structure determination and magnetic properties of a new complex, phenethylammonium tetrachloromanganate(II), (C(6)H(5)CH(2)CH(2)NH(3))(2)MnCl(4) (Mn-PEA). Single crystals of Mn-PEA were obtained from methanol solution using the solvent-evaporation method at room temperature. The crystal structure of Mn-PEA was determined by single-crystal X-ray diffraction (orthorhombic, space group Pbca, a = 7.2075(9), b = 7.3012(14), c = 39.413(6) ? and Z = 4). The structure consisted of an extended [MnCl(4)](2-) network and two phenethylammonium cations to form a two-dimensional halide perovskite structure. Temperature-dependent magnetization measurements indicated that Mn-PEA acted as a weak ferromagnet below T(C) = 44.3 K due to spin canting. Below T(C), the magnetic behavior differed significantly from the behavior commonly observed among weak ferromagnets. The susceptibility depended strongly on the crystal orientation, the external magnetic field strength, and the magnetic history. The isothermal magnetization for two orientations revealed a ferromagnetic moment with a spin-canting angle of 0.04° and a spin-flop transitions with H(sf) = 3.5 T. The weak ferromagnetism, which manifested as spontaneous magnetization and magnetic hysteresis near a field strength of zero, was driven by interplay between the easy axis and the antisymmetric Dzyaloshinsky-Moriya (DM) interaction, leading to directional dependent magnetic behavior.     

Chemically induced magnetism and magnetoresistance in La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4)

It is shown by magnetometry and microSR spectroscopy that short-range magnetic interactions between the Mn cations in the nonmetallic K(2)NiF(4)-like phase La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4) become significant below approximately 200 K. Negative magnetoresistance (rho/rho(0) approximately 0.5 in 14 T at 108 K) is apparent below this temperature. Neutron diffraction has shown that an applied magnetic field of 5 T is sufficient to induce saturated (3.38(7)mu(B) per Mn) long-range ferromagnetic ordering of the atomic moments at 2 K, and that the induced ordering persists up to a temperature of 50 K in 5 T. Spin glass behavior is observed below 20 K in the absence of an applied field. The induced magnetic ordering is attributed to the subtle changes in band structure brought about by the external field, and to the controlling influence of Rh(3+) over the relative strength of competing magnetic exchange interactions.     

Magnetic and Structural Characterizations of Co-based Heusler Nanoparticles Fabricated via Simple Co-precipitation Method

Nanoparticles of Co₂FeAl magnetic alloy was successfully fabricated in the presence of a well-known capping agent, polyvinyl alcohol, as a polymer template. The magnetic properties were studied using hysteresis curve and first-order reversal curve (FORC) measurements at room temperature. FORC diagrams demonstrated a wide distribution of the coercive field owing to the presence of different particle sizes in products. TEM image also showed that the synthesized samples are composed of some large clusters containing a few smaller particles. The maximum value of magnetization (~76 emu/g) and coercivity (573 Oe) were obtained in the annealed sample with 5 °C/min. A wider distribution of grain size with a smaller average of 20.5 nm as well as lower-degree of crystallinity was observed in the sample annealed with higher rate of 10 °C/min.     

Magnetic properties of nm-sized iron crystallites and clusters embedded in vacuum-deposited MgO films

Magnetic property of single crystalline iron-MgO composite films was measured with a SQUID magnetometer. The thermo-magnetic (M-T) curves showed splitting of the magnetization in low temperature, depending on zero-field cooling and field cooling cases. The magnetization (M-H) curves at 5 K after the zero-field cooling showed hysteresis with larger coercive force than that of bulky iron. Systematic study of the relationship between the structure of the composite films and the magnetic property showed that nm-sized iron crystallites embedded epitaxially in MgO films play a main role to the property.     

外加磁场条件下镍纳米材料的形貌可控制备

在常压下,采用外加磁场辅助的液相还原法制备得到了直径约为250 nm镍纳米晶纤维。磁性能测试结果表明镍纤维的饱和磁化强度为8.94 emu·g^-1,矫顽力为133.8 Oe,说明得到的镍纤维具有铁磁性能。此外,还研究了溶剂种类对产物微观结构和形貌的影响。结果表明,产物的形貌受溶剂种类的影响十分明显,只有分子结构中含有2个端羟基的醇类溶剂才可以用来制备形貌均一的超细镍纤维。     

High-pressure synthesis and neutron diffraction investigation of the crystallographic and magnetic structure of TeNiO3 perovskite

TeNiO(3) has been prepared under moderate pressure conditions (3.5 GPa), starting from a reactive TeO(2) and Ni(OH)(2) mixture contained in a sealed platinum capsule under the reaction conditions (850 °C for 2 h). The sample has been studied by neutron powder diffraction (NPD) data and magnetization measurements. TeNiO(3) crystallizes in an orthorhombically-distorted perovskite structure (space group Pnma) with the unit cell parameters a = 5.9588(1) ?, b = 7.5028(1) ? and c = 5.2143(1) ?. The NiO(6) octahedral network is extremely tilted, shaping a trigonal-pyramidal environment for the Te, where it is effectively coordinated to three oxygen atoms at Te-O distances of 1.92 ?. Below T(N) ≈ 130 K, it experiences an antiferromagnetic ordering, as demonstrated by susceptibility and NPD measurements. Above the Néel temperature, a paramagnetic moment of 3.24(1) μ(B)/f.u. and θ(Weiss) = -199(1) K are obtained from the reciprocal susceptibility. Below T(N), the magnetic reflections observed in the neutron patterns can be indexed with a propagation vector k = 0. The magnetic structure corresponds to the magnetic mode G(y)F(z). The magnetic moments are oriented along the y-direction, with a canting along the z-axis. This ferromagnetic component explains the weak ferromagnetism observed in the magnetization isotherms; the infrequent shape of the magnetization cycles suggests a metamagnetic transition below 0.2 T. At T = 2.5 K, the ordered magnetic moment for the Ni(2+) ions is 1.88(5) μ(B) for the G(y) mode and 0.9(2) μ(B) for the F(x) mode.     

Nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate: a metal-organic ferromagnetic dye

The new metal-organic compound nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate, i.e. Ni(2)[(PDI-BP)(H(2)O)(2)]·3H(2)O (1), has been synthesized and its structural and magnetic properties have been studied. Reaction of 3,4;9,10-perylenediimide bis-phosphonate (PDI-BP, hereafter) ligand and nickel chloride in water resulted in the precipitation of a red and poorly crystalline solid (1). As the solid shows a poor crystalline organization of aggregates, the energy dispersive X-ray diffraction analysis (EDXD) technique has been used to obtain short-range order structural information of the single nanoaggregates by radial distribution function analysis. The overall structure of the compound is characterized by layers containing perylene planes shifted in the direction perpendicular to the stacking axes in such a way that only the outer rings overlap. The edges of the perylene planes are connected to the phosphonate groups through an imido group. The oxygen atoms of the [-PO(3)](2-) group and those of the water molecules are bonded to the nickel ions resulting in a [NiO(6)] octahedral coordination sphere. The Ni-O bond lengths are 0.21 ± 0.08 nm and the Ni-O-Ni angles of aligned moieties are 95 ± 2°. The oxygen atoms of the water molecules and the nickel atoms are nearly planar and almost perpendicular to the perylene planes forming chains of edge-sharing octahedra. The magnetic properties of (1) show the presence of intrachain ferromagnetic Ni-Ni interactions and a long-range ferromagnetic order below 21 K with a canting angle and with a spin glasslike behavior due to disorder in the inorganic layer. Hysteresis cycles show a coercive field of ca. 272 mT at 2 K that decreases as the temperature is increased and vanishes at ca. 20 K.     

Hydrothermal synthesis in the system Ni(OH)(2)-NiSO(4): nuclear and magnetic structures and magnetic properties of Ni(3)(OH)(2)(SO(4))(2)(H(2)O)(2)

We present the synthesis, characterization by DT-TGA and IR, single crystal X-ray nuclear structure at 300 K, nuclear and magnetic structure from neutron powder diffraction on a deuterated sample at 1.4 K, and magnetic properties as a function of temperature and magnetic field of Ni(3)(OH)(2)(SO(4))(2)(H(2)O)(2). The structure is formed of chains, parallel to the c-axis, of edge-sharing Ni(1)O(6) octahedra, connected by the corners of Ni(2)O(6) octahedra to form corrugated sheets along the bc-plane. The sheets are connected to one another by the sulfate groups to form the 3D network. The magnetic properties measured by ac and dc magnetization, isothermal magnetization at 2 K, and heat capacity are characterized by a transition from a paramagnet (C = 3.954 emu K/mol and theta = -31 K) to a canted antiferromagnet at T(N) = 29 K with an estimated canting angle of 0.2-0.3 degrees. Deduced from powder neutron diffraction data, the magnetic structure is modeled by alternate pairs of Ni(1) within a chain having their moments pointing along [010] and [010], respectively. The moments of Ni(2) atoms are oppositely oriented with respect to their adjacent pairs. The resulting structure is that of a compensated arrangement of moments within one layer, comprising one ferromagnetic and three antiferromagnetic superexchange pathways between the nickel atoms.     

Magnetic properties and structures of equiatomic rare earth-platinum compounds RPt (R = Gd,Tb, Dy,Ho, Er,Tm)

The magnetic properties and structures of RPt compounds (R = Gd, Tb, Dy, Ho, Er, and Tm) are presented. Below their Curie temperature the compounds exhibit ferromagnetic behavior. In GdPt, the spontaneous magnetization at 4.2°K ($\text{6.7 μ}{}_{\mathrm{<mtext>B</mtext>}}\text{Gd}$) and the small superimposed susceptibility suggest that the gadolinium moments are parallel and the exchange interactions are positive. In the three types of noncollinear magnetic structures observed in the other compounds the rare earth atoms are divided into two sublattices with different magnetization directions. They give rise to a ferromagnetic component associated with an antiferromagnetic component. These structures, which are analyzed in terms of crystal field effects, result from a competition between a magnetocrystalline anisotropy and positive exchange interactions of Heisenberg type.     

Room-temperature ferromagnetism in pure ZnO nanoflowers

ZnO nanoflowers are synthesized by hydrothermal method. The morphology of ZnO is captured by SEM, TEM and HRTEM, which is composed of closely packed nanorods of about 100 nm in diameter and 1 μm in length. The ZFC/FC curves show superparamagnetic features. The abnormal increase in magnetization curves below 14 K comes from the isolated vacancy clusters with no interaction. The magnetic hysteresis at 300 K displays saturation state and confirms room-temperature ferromagnetism. While the magnetic hysteresis at 5 K shows nonsaturation state due to the enhanced effects of vacancy clusters. The O 1s XPS results can be fitted to three Gaussian peaks. The existence of medium-binding energy located at 531.16 eV confirms the deficiency of O ions at the surface of ZnO nanoflowers.     

A composite of polyaniline with both conducting and ferromagnetic functions

A composite of polyaniline (PANI) with both conducting and ferromagnetic functions was synthesized by a chemical method proposed by the authors. For the electrical properties, its room-temperature conductivity was measured to be about 10⁻¹ S/cm when doped with 1.0M HCl, and it is independent of the preparation conditions, such as reaction temperature and concentration of FeSO₄ solution. Temperature dependence of the conductivity of the composites at temperature between 77 and 450 K is controlled by thermal activation and dedoping processes, which result in the decrease of conductivity with increase of temperature as T > 320 K. For their magnetic properties, unusual ferromagnetic properties with high saturated magnetization (M₂) and lower coercive force (H_c = 0) were observed. An effect of the preparation conditions on the ferromagnetic properties of composites was observed. The higher the reaction temperature and the concentration of FeSO₄ solution, the higher the saturated magnetization was observed. No hysteresis feature (i.e. H_c = 0) for any PANI composites synthesized in this paper was observed, and this is independent of the preparation conditions. This may be attributed to the nanometer size of the magnetic particles existing in composites. Thus, it suggests that the doping of PANI leads to electrical properties of composites, whereas the nanocrystalline magnetic particles (Fe₃O₄) are responsible for the observed ferromagnetic properties of PANI composites. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2129–2136, 1997     

Magnetic structure of Ni(DCOO)2(D2O)2

Ni(HCOO)(2)(H(2)O)(2) is a structurally simple coordination polymer showing interesting magnetic phase transitions at low temperature (<16K). Previously published studies of these phase transitions have yielded inconsistent results, questioning the correctness of the published magnetic structure. Here heat capacity and magnetic susceptibility of a fully, a partly and a non-deuterated sample were measured, and they all exhibit magnetic phase transitions around 3 and 15 K. Neutron powder diffraction data was collected on the fully deuterated sample at various temperatures between 1.5 and 25 K. A magnetic model was refined against the neutron diffraction data using a spin system composed of two canted antiferromagnetic sublattices. The magnetic moments of the two sublattices show different magnitude, 1.7 μ(B) and 1.3 μ(B), and the temperature dependence of the magnetic sublattices is quite different. One of the sublattices shows the expected temperature behavior of an antiferromagnetic compound whereas the other sublattice follows a Brillouin like function with a slowly increasing magnetization below the Ne?el temperature.