- Coordination compounds of nickel(II) salts with substituted pyridines. Complexes of 2-, 3-, and 4-methylpyridine
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Complexes of 2-, 3-, and 4-methylpyridine (2-pic, 3-pic, and 4-pic) with a number of Ni(II) salts (chloride, bromide, iodide, nitrate, perchlorate, and tetrafluoroborate) were prepared and investigated. Three series of complexes were obtained, Ni(pic)X2 (pic = 2-pic, 3-pic; X = Cl, Br); Ni(pic)2X2 (pic = 2-pic, 3-pic, 4-pic; X = Cl, Br, I, NO3); Ni(pic)4X2 (pic = 3-pic, 4-pic; X = Cl, Br, I, NO3, ClO4, BF4). The complex Ni(3-pic)4X2 (X = ClO4, BF4) was obtained in two isomeric forms, identified as [Ni(3-pic)4X2] and [Ni(3-pic)4]X2, respectively. The complexes of 4-aminopyridine, Ni(4-NH2py)4X2 (X = Cl, Br, I, ClO4), were also prepared and investigated. The stoichiometry and stereochemistry of the complexes were correlated with the properties of the anion and ligand, in particular with the basicity and steric requirements of the latter.
- Vallarino,Hill,Quagliano
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- Preparation, characterisation and thermal behaviour of N-(3-aminopropyl)-1,3-propanediamine complexes of nickel(II) in the solid state
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The complexes [Ni(dpt)2]X2.nH2O (where dpt is N-(3-aminopropyl)1,3-propanediamine; n = 0 when X is I, NCS or ClO4; n = 1 when X is Cl, Br or NO3; n = .mchgt. 1 when X is 0.5SO4 and 0.5SeO4), Ni(dpt)X2.nH2O (n = 0 when X is Cl or NO3; n = 1 when X is Br or
- Pariya, Chandi,Ghosh, Ashutosh,Chaudhuri, Nirmalendu Ray
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- How Inert, Perturbing, or Interacting Are Cryogenic Matrices? A Combined Spectroscopic (Infrared, Electronic, and X-ray Absorption) and DFT Investigation of Matrix-Isolated Iron, Cobalt, Nickel, and Zinc Dibromides
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The interactions of FeBr2, CoBr2, NiBr2, and ZnBr2 with Ne, Ar, Kr, Xe, CH4, and N2 matrices have been investigated using IR, electronic absorption, and X-ray absorption spectroscopies as well as DFT calculations. ZnBr2 is linear in all of the matrices. NiBr2 is linear in all but N2 matrices, where it is severely bent. For FeBr2 and CoBr2 there is a more gradual change, with evidence of nonlinearity in Xe and CH4 matrices as well as N2. In the N2 matrices, the presence of νNN modes blue-shifted from the "free" N2 values indicates the presence of physisorbed species, and the magnitude of the blue shift correlates with the shift in the ν3 mode of the metal dibromide. In the case of NiCl2 and NiBr2, chemisorbed species are formed after photolysis, but only if deposition takes place below 10 K. There was no evidence for chemisorbed species for NiF2 and FeBr2, and in the case of CoBr2 the evidence was not strong.
- Wilkin, Owen M.,Harris, Neil,Rooms, John F.,Dixon, Emma L.,Bridgeman, Adam J.,Young, Nigel A.
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- Thermal studies of 2-aminoethanol complexes of nickel (II) in the solid state
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[NiL3]X2 (where L = 2-aminoethanol and X is Cl-, Br-, I-, NO3-, 0.5SO42- or 0.5SeO42-) and [NiL2X2] (X is Cl-, Br-, or SCN-) have been synthesised from solution and their thermal study has been carried out in the solid phase. [NiL3]I2 and [NiL3]SeO4 undergo reversible endothermic phase transitions upon heating (63-93°C and 94-113°C, respectively, for heating and 94-65°C and 110-190°C, respectively, for cooling), whereas [NiL3](NO3)2 exhibits two successive reversible endothermic phase transitions (10-38°C and 50-62°C for heating and 56-48°C and 19 - (-8)°C for cooling). On the other hand, [NiL3]SO4 undergoes irreversible endothermic phase transition (99-112°C) in the solid state. All these transformations are assumed to be associated with the conformational changes of 2-aminoethanol chelate rings. [NiL2(NCS)2] melts at ～ 168°C and remains supercooled for a few days at ambient temperature. The initial temperatures of decomposition (Ti) of these complexes have been compared with those of the corresponding ethane-1, 2-diamine complexes of nickel (II).
- Das, Debasis,Ghosh, Ashutosh,Koner, Subratanath,Ray Chaudhuri, Nirmalendu
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- Insight into the mechanism of thermal stability of α-diimine nickel complex in catalyzing ethylene polymerization
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The union of experimental and computational methods can accelerate the development of polymerization catalysts for industrial applications. Herein, we report complementary experimental and computational studies of the thermal stability of α-diimine nickel complexes by using thermally stable Cat. 1 and a typical Brookhart catalyst (B-Cat) as models. Experimentally, we found that many more nickel atoms could be activated for Cat. 1 at elevated temperature during the ethylene polymerization process compared to those for B-Cat. Computationally, first-principle calculations showed that the decomposition energies of Cat. 1 were found to be higher than those of B-Cat, contributing to the activation observed for Cat. 1. We found that the presence of ethydene evidently affected the conformation of C1-N1-Ni-N2-C2 five-membered ring (where the nickel center is located) of Cat. 1, turning the envelope conformation (B-Cat) into a half-chair conformation (Cat. 1). According to calculations, the decomposition energy of the latter was 17.4 kJ/mol higher than that of the former. These results provide information to elucidate the mechanism of thermal stability of α-diimine nickel catalyst and significantly advance the development of thermally stable α-diimine nickel catalysts used in industry.
- Zhu, Liang,Zang, Dandan,Wang, Yi,Guo, Yintian,Jiang, Baiyu,He, Feng,Fu, Zhisheng,Fan, Zhiqiang,Hickner, Michael A.,Liu, Zi-Kui,Chen, Long-Qing
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- Microwave-assisted carbohydrohalogenation of first-row transition-metal oxides (M = V, Cr, Mn, Fe, Co, Ni, Cu) with the formation of element halides
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The anhydrous forms of first-row transition-metal chlorides and bromides ranging from vanadium to copper were synthesized in a one-step reaction using the relatively inexpensive element oxides, carbon sources, and halogen halides as starting materials. The reactions were carried out in a microwave oven to give quantitative yields within short reaction times.
- Berger, Matthias,Neumeyer, Felix,Auner, Norbert
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supporting information
p. 11691 - 11693
(2013/11/19)
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- Polymer complexes. LIV. Structural and spectral studies of supramolecular coordination polymers built from Ni(II), Fe(II) and Pd(II) with sulphadrug
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Polymer complexes of p-acrylamidyl sulphaguanidine (HL) with Ni(II), Fe(II) and Pd(II) salts have been prepared. The structures of the polymer complexes were elucidated using elemental analysis, 1H NMR, UV-Vis, IR spectroscopies, magnetic moment, molar conductance and thermal analysis. The polymer complexes were isolated in 1:1 and 1:2 (M:L) ratios. The solid monocomplexes (1:1) (M:L) were isolated in the general formula [Fe(HL)O 2SO2(OH2)2]. The biscomplexes (1:2) (M:L) solid chelates found to have the general formula [Ni(HL)2X 2]n (X = Cl-, Br-, I-, NO3, NCS- ), [Fe(HL)(en)(OSO3)(OH 2)]n and [Ni(HL)2(Py)2] nX2, while {[Pd(L)X]2}n (1:1) (X = Cl- or Br-). In all the polymer complexes the ligand and anions were found to be coordinated to the Ni(II) and Fe(II) ions. The bidentate nature of the ligand is evident from IR spectra. The magnetic and spectroscopic data indicate a octahedral geometry for complexes. The thermal behaviour of these chelates shows that the hydrated complexes loss water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps.
- El-Sonbati,Belal,Diab,Mohamed
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- Reactions of a phosphinoimino-thiazoline-based metalloligand with organic and inorganic electrophiles and metal-induced ligand rearrangements
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The reaction of the neutral Pt(II) bischelated complex cis-[Pt{Ph 2PNA·A·A·CA·A·A·NCH 2CH2S}2] ([Pt(2-H)2], 1; 2 = Ph2PNHC=NCH2CH2S, N-(diphenylphosphino)- thiazoline-2-amine) with the organic electrophile EtN=C=S yielded complex [Pt(2-H)(2-HA·EtNCS)] (3) as a result of the nucleophilic attack of the coordinated 2-((diphenylphosphino)imino)thiazolidin- 3-yl moiety on the heteroallene carbon atom and coordination of the sulfur atom to the metal. The reaction of 1 with [Cu(NCMe)4]PF6 also proceeded by nucleophilic attack of the P-N nitrogen atom on Cu(I) and afforded the coordination polymer [1·Cu]∞[PF6] ∞ (4). The reaction of ligand 2 with NiBr2· xH2O resulted in a molecular rearrangement and afforded an unexpected pentacoordinated diamagnetic complex, [Ni(2){trans-Ph2PN=C- N(PPh2)CH2CH2S}Br]Br (6), which likely arises from a metal-templated ligand coupling in the presence of water acting as promoter. Complex 6 was evaluated as a precatalyst for ethylene oligomerization, showing good activities with EADC as cocatalyst. All new complexes were structurally characterized by X-ray diffraction.
- Zhang, Shuanming,Pattacini, Roberto,Braunstein, Pierre
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p. 6660 - 6667
(2011/03/17)
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- Mono- and dinuclear nickel complexes with phosphino-, phosphinito-, and phosphonitopyridine ligands: Synthesis, structures, and catalytic oligomerization of ethylene
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The P,N-type ligands 2-[(diphenylphosphino)methyl]pyridine (12), 2-[2-(diphenylphosphino)ethyl]pyridine (13), 2-methyloxy(diphenylphosphino) pyridine (14), 2-methyloxy(dibenzyl-1,2-oxaphosphorino)pyridine (15), and 2-methyloxy(di-tert-butylphosphino)pyridine (16) have been prepared in good yields, and 12 and 13 have been used to synthesize Ni(II) complexes of formula [Ni(P,N)Cl2], 17 (P,N = 12) and 18 (P,N = 13), by reaction with NiCl2 in methanol. The crystal structure of 18 has been determined by X-ray diffraction to be dinuclear with a distorted square-base pyramidal geometry around the Ni(II) centers. To examine the possible influence of the nature of the spacer link between the P and N donor atoms, we compared ligand 13, with a CH2CH2 spacer, with 14 and 16, which have a isosteric CH2-O spacer. Reactions of the phosphinitopyridine ligands 14 and 16 and of the phosphonitopyridine 15 with [NiX2(DME)] (X = Cl or Br) afforded the complexes [Ni(P,N)Cl2] 20 (X = Cl; P,N = 14), 21 (X = Br; P,N = 14), 22 (X = Cl; P,N = 16), and 23 (X = Cl; P,N = 15), respectively. The mononuclear structure of complex 22 has been established by X-ray diffraction and showed a distorted tetrahedral geometry around the metal center. Complexes 17, 18, and 20-22 have been tested as precatalysts in the oligomerization of ethylene, with AlEtCl2 or MAO as cocatalyst, in order to evaluate the influence of the stereoelectronic properties of the phosphorus substituents. With only 6 equiv of AlEtCl2 as cocatalyst and 4 × 10-5 mol precatalyst, complex 18 was the most active, with turnover frequencies (TOF) up to 91 200 C2H4/(mol Ni·h), and 20 with 2 equiv of AlEtCl2 showed the highest selectivities for ethylene dimers (up to 97%) and in 1-butene (up to 72%). When only 10-5 mol precatalyst was used, the TOF values went up to 207 600 for 18 and 150 100 for 20. With only 25 equiv of MAO as cocatalyst, complex 18 was again the most active, with TOF values up to 20 600 C2H 4/(mpl Ni·h). Despite the high selectivity for C4 olefins of 17, 18, 20, and 21 (up to 93% for 20), 22 presented the best selectivities for 1-butene (up to 73%) with MAO as cocatalyst, and its high reactivity for the reinsertion of 1-butene resulted in 2-ethyl- 1-butene being the main product of the catalytic reaction (up to 91%).
- Kermagoret, Anthony,Braunstein, Pierre
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- Aggregation of [(tBu3SiS)MX]: Structures of {[Br 2Fe(μ-SSitBu3)2FeBr(THF)]Na(THF) 4}∞, cis[(THF)Fel]2(μ-SSitBu 3)2
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A convenient synthesis of tBu3SiSH and tBu3SiSNa(THF)x led to the exploration of tBu3SiSMX aggregation. The dimer, [( tBu3SiS)Fe]2(μ-SSitBU 3)2 (12), was formed from [{(Me 3Si)2N}Fe]2(μ-N(SiMe3) 2)2 and the thiol, and its dissolution in THF generated (tBu3SiS)2Fe(THF)2 (1-(THF) 2). Metathetical procedures with the thiolate yielded aggregate precursors [X2Fe](μ-SSitBu3) 2[FeX(THF)]Na(THF)4 (3-X, X = Cl, Br) and cis-[(THF)IFe]2(μ-SSitBu3)2 (4). Thermal desolvations of 3-Cl, 3-Br and 4 afforded molecular wheels [Fe(μ-X)(μ-SSitBu3)]12(C 6H6)n (5-FeX, X = Cl, Br) and the ellipse [Fe(μ-l)(μ-SSitBu3)]14(C 6H6)n (6-Fel). Related metathesis and desolvation sequences led to wheels [Co(μ-Cl)(μ-SSitBu 3)]12(C6H6)n (5-CoCl) and [Ni(μ-Br)(μ-SSitBu3)]12(C 6H6)n (5-NiBr). The nickel wheel disproportionated to give, in part, [(tBu3SiS)Ni] 2(μ-SSitBu3)2 (7), which was also synthesized via salt metathesis. X-ray structural studies of 12 revealed a roughly planar Fe2S4 core, while 1-(THF) 2, 3-Br, and 4 possessed simple distorted tetrahedral and edge-shared tetrahedral structures. X-ray structural studies revealed 5-MX (MX = FeCl, FeBr, CoCl, NiBr) to be wheels based on edge-shared tetrahedra, but while the pseudo-D6d wheels of 5-FeCl, 5-CoCl, and 5-FeBr pack in a body-centered arrangement, those of pseudo-C6v 5-NiBr exhibit hexagonal packing and two distinct trans-annular d(Br...Br). Variable-temperature magnetic susceptibility measurements were conducted on 5-FeCl, 5-CoC, 5-FeBr, and 6-Fel, and the latter three are best construed as weakly antiferromagnetic, while 5-FeCl exhibited modest ferromagnetic coupling. Features suggesting molecular magnetism are most likely affiliated with phase changes at low temperatures.
- Sydora, Orson L.,Henry, Thomas P.,Wolczanski, Peter T.,Lobkovsky, Emil B.,Rumberger, Evan,Hendrickson, David N.
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p. 609 - 626
(2008/10/09)
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- Chemical bond and hybridization in nickel compounds
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By means of ultraviolet reflectance and valence band photoemission one can get a scale of ionicity for nickel halides. The fraction of ionic character of the chemical bond, from 0.72 in NiI2 to 0.80 in NiCl2, evaluated with the Phillips theory has been related to the ground state d electron counts ?ndn? calculated from Ni2p core photoemission. While the chemical trends of cluster model parameters are in general well reproduced, a systematic discrepancy in band gap values (2-3 eV) has been found by comparing core-level results with optical and photoconductivity data.
- Pollini I.
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- Primary aliphatic amine complexes of transition-metal halides: III. Thermal and spectroscopic characterization of solid methylamine complexes of nickel(II) halides
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The hexakis(methylamine) complexes of nickel(II)-chloride, -bromide and -iodide have been prepared using-gas phase preparation procedure. The thermal decomposition starts with the release of four moles of the organic ligand. The bis(methylamine) intermediate decomposes in one step to the pure nickel(II) halide in the case of the chloride compound, however one and a half moles of methylamine containing intermediates were identified for the bromide and iodide analogues. The UV/VIS and the far IR spectra of the hexakis complexes show a typical octahedral environment around the central nickel(II) ion.
- Kenessey,Carson,Allan,Wadsten,Liptay
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p. 167 - 173
(2008/10/08)
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- Synthesis of some 3d-Metal Complexes of 2,6-Diacetylpyridine(benzyl and acetone)hydrazone
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2,6-Diacetylpyridine bis(benzyl and acetone)hydrazone and some 3d-metal complexes have been prepared. These complexes are five-coordinated trigonal bipyramidal. The ligand coordinates through the pyridine-N and amide-N. Formation of two chelate rings by one molecule of ligand, is a feature that undoubtedly enhances the stability of the complexes.
- Singh,Ansari,Rana
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p. 448 - 451
(2007/10/03)
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- Thermal studies of N-propylethane-1,2-diamine and N-isopropylethane-1,2-diamine complexes of nickel(II) in the solid state
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[NiL3]X2 · 2H2O (X is Cl-, Br- and ClO-4; L is N-propylethane-1,2-diamine), [NiL2(H2O)2](ClO4)2, [NiL2X2] (X is Cl-, Br-, 0.5SO2-4 and 0.5SeO2-4), [NiL12(H2O)2](ClO4) 2 · 2H2O (L1 is N-isopropylethane-1,2-diamine), [NiL12X2] (X is Cl-, Br-, NCS- and O.5SeO2-4) and [NiL12SO4] · 3H2O have been synthesised from solution and their thermal studies have been carried out in the solid phase. [NiL2X2] (X is Cl- and Br-), NiLCl2 and NiL1SO4 have been prepared pyrolytically from their respective parent species in the solid state. [NiL2](ClO4)2 and [NiL12](ClO4)2 were prepared pyrolytically from their parents species, and also by storing [NiL2(H2O)2](ClO4)2 and [NiL12(H2O)2](ClO4) 2 · 2H2O in a CaCl2 desiccator, respectively; these transformations are accompanied by a pink to yellow colour change due to octahedral to square-planar configurational changes. All other bis(diamine) species have octahedral geometry. Among them, [NiL2X2] (X is Cl- and Br-) and [NiL12X2] (X is Cl-, Br- and NCS-) possess trans-octahedral configuration, whereas [NiL2X] (X is SO2-4 and SeO2-4), [NiL12SO4] · 3H2O and [NiL12SeO4] have cis-configuration. On heating, trans-[NiL12 Br2] and trans-[NiL12(NCS)2] undergo reversible endothermic phase transitions (86-99°C, ΔH = 0.52 kJ mol-1 for heating, and 92-81°C, ΔH = - 0.53 kJ mol-1 for cooling for the former, and 162-224°C, ΔH = 0.27 kJ mol- for heating and 208-150°C, ΔH = - 0.25 kJ mol-1 for cooling for the latter), most likely due to conformational changes of the diamine chelate rings.
- Das, Debasis,Ghosh, Ashutosh,Chaudhuri, Nirmalendu Ray
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p. 155 - 163
(2008/10/09)
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- Thermal studies of N,N′-diethylethane-1,2-diarnine complexes of nickel(II) in the solid state
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NiL2X2·nH2O (where L = N,N′-diethylethane-1,2-diamine; n = 2 when X is Cl-, Br-, I-, NO3-, 0.5SO42-, 0.5SeO42- or CF3SO3-; n = 0 when X is CF3CO2- or CCl3CO2-) have been synthesised from solution and investigated by TG-DTA and DSC in the solid state. All the hydrated complexes have trans octahedral geometry and on heating undergo dehydration-anation reactions. The dehydrated complexes are also trans octahedral, except NiL2X2 (X is NO3-, 0.5SO42- or 0.5SeO42-) for which cis octahedral geometry is proposed. [NiL2(H2O)2]X2 (X is Br- or CF3SO3-) shows thermochromism (blue → green) upon dehydration. NiL2X2 (X is Cl-, Br-, 0.5SO42- or 0.5SeO42-) yield mono-diamine species in the solid state on heating. NiL2SO4 undergoes a reversible phase transition (heating cycle, 178-193°C, ΔH = - 4.0k J mol-1; cooling cycle, 186-172°C; ΔH = 4.0kJ mol-1) without a visual colour change.
- Pariya, Chandi,Ghosh, Ashutosh,Chaudhuri, Nirmalendu Ray
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p. 185 - 193
(2008/10/09)
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- THERMAL DECOMPOSITION OF NICKEL(II) BROMIDE IN SODIUM NITRATE-POTASSIUM NITRATE EUTECTIC MELT
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Nickel bromide generally decomposes at a very high temperature whereas in NaNO3 - KNO3 eutectic melt it decomposes at 260 deg C forming NiO, NO2, O2 and Br2.In the reaction between NiBr2 and nitrate melt probably nitrate ions enter the crystal lattice of NiBr2 where the force of attraction is lowest.
- Singh, Nakshatra Bahadur,Pandey, Sheo Pujan,Kumar, Pushp
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p. 241 - 246
(2007/10/02)
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- STUDIES ON TRANSITION-METAL PICOLINE COMPLEXES - I. PREPARATION AND THERMOANALYTICAL INVESTIGATIONS.
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A large number of transition-metal picoline halides were prepared, and their thermal decompositions were investigated by TG, DTG, DTA and thermomicroscopy. The compounds were classified on the basis of their thermal properties and two possible mechanisms of thermal decomposition were established.
- Liptay,Borbely-Kuszmann,Nagy
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- Macrocyclic Complexes: Part XI - Macrocyclic Complexes of Cobalt(II) and Nickel(II) with 1,4,5,7,8,11,12,14-Octaazacyclotetradeca-1,3,8,10-tetraene
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A series of macrocyclic complexes of cobalt(II) and nickel(II) with the ligand tetraeneN8 have been isolated by the action of formaldehyde on bis-glyoxal dihydrazone chelates of cobalt(II) and nickel(II).The reaction is proton catalysed and the coordination template effect governs the steric course of the reaction.The structures of the complexes have been elucidated on the basis of IR and electronic spectral data and magnetic properties.For each of the complexes, a well-defined reduction wave corresponding to the formation of species where the metal ion can be formally assigned an oxidation state +1 has been observed.The reduction for each macrocycle is more anodic, which is of the order 0.3 V, compared to that for its parent nonmacrocyclic complexes.
- Sahoo, Bhagirathi,Rout, A. K.,Sahoo, B.
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p. 609 - 614
(2007/10/02)
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- Hydrogenation process
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Process for the hydrogenation of functionally substituted acetylenic compounds employing catalyst comprising nickel boride on an inorganic oxide support is disclosed. Functionally-substituted acetylenic compounds are selectively reduced under mild reaction conditions to give functionally-substituted cis-olefinic compounds in high yield.
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- NICKELOCENE CHEMISTRY IV. NEW NICKELACYLES (η-C5H5)>PF6 (n = 1-3) FROM REACTIONS OF NICKELOCENE AND WITH BIS-YLIDS
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Nickelocene reacts with the bis-ylids, Ph3PCH(CH2)nCHPPh3 (n = 1-3) to give the new chelate complexes (η-C5H5)>PF6.The same compounds are also formed on reaction of the bis-ylids with .The compounds with ring siz
- Booth, Brian L.,Smith, Kenneth G.
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p. 229 - 237
(2007/10/02)
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- Symmetrically disubstituted ferrocenes. III. Complexes of ferrocene-1,1′-bis(dimethylarsine) and ferrocene-1,1′-bis(diphenylarsine) with the group VIII metals
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The chemistry of the ditertiary arsines ferrocene-1,1′-bis(dimethylarsine) (fdma) and ferrocene-1,1′-bis(diphenylarsine) (fdpa) functioning as ligands toward the metals of group VIII has been explored. The complexes M(fdma)X2 (M = Pd; X = Cl, Br and M = Pt; X = Cl, Br, I) react with an excess of the diarsine fdma to produce solutions from which salts of the five-coordinate M(fdma)2X+ ions and the four-coordinate M(fdma)22+ ions can be isolated. Reactions of this type do not occur for the more sterically crowded diarsine fdpa. The simple complexes (fdma)NiX2 (X = Cl, Br, and I) and (fdpa)NiX2 (X = Cl, Br) could not be prepared by a number of routes. One of these, however, the reaction of (diars)Ni(CO)2 with iodine, led to the isolation of the species (diars)Ni(CO)I2 (where diars = fdma or fdpa). These seem to be examples of carbonyl complexes of nickel in the +2 oxidation state.
- Bishop,Davison
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p. 832 - 837
(2008/10/08)
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- Transition metal complexes of secondary phosphines. III. Four- and five-coordinate complexes of nickel(II) halides with diphenylphosphine
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The reactions of diphenylphosphine with nickel halides in nonionizing solvents have yielded trans-[NiI2(HP(C6H5)2)2] and the five-coordinate complexes [NiI2(HP(C6H5)s
- Hayter
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p. 932 - 935
(2008/10/08)
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- On the magnetic properties of a CrBr3 single crystal
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Magnetic properties of single crystals of CrBr3 have been measured with a magnetic balance and also with a torque magnetometer. The ferromagnetic Curie point has been found to be 37°K from the temperature dependences of magnetization and of torque. Based on the data of the magnetic susceptibility above the Curie point, the paramagnetic Curie point θp, Curie constant CM and the effective Bohr magneton number have been determined to be 47°K, 1.84 and 3.85 μB respectively. From the saturation magnetization at 4 2°K, the moment of chromium ion is estimated to be 3 μB. coinciding with the spin moment obtained from the susceptibility measurement above the Curie temperature. Direction of easy magnetization lies along the c-axis of the hexagonal lattice, and the second order and the fourth order anisotropy constants are estimated to be K1= -5.08×105 and K2 = 0.65×105 erg/cc respectively. In the present results, there is found a small deviation in the torque curves from simple sinusoidal form, L = K sin 2θ, which is discussed on the basis of the higher order term of magnetic anisotropy in the high field strength range and also of the domain-theoretical consideration in the low field strength range.
- Tsubokawa, Ichiro
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p. 1664 - 1668
(2008/10/08)
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