Magnetic Studies in Mixed-Metal Valency Molecule Magnets NBu4FeιιnMnιι1-n[Feιιι(OX)3](n=0.03, 0.10, 0.15, 0.97)

2012 ◽  
Vol 567 ◽  
pp. 259-262 ◽  
Author(s):  
Qing Lin ◽  
Shao Hong Chen ◽  
Yun He ◽  
Xiao Gang Li ◽  
Hai Fu Huang
Keyword(s):  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Magnetization Curves ◽  
Magnetic Studies ◽  
Magnetic Exchange Interaction ◽  
Magnetic Exchange ◽  
Mixed Valency ◽  
Bridging Ligand ◽  
Bifurcation Phenomenon ◽  
Oxalate Group

The mixed valency character and antiferromagnetic coupling in Molecule magnets Materials NBu4FeIInMnII1-n[FeIII(OX)3]（n=0.03、0.10、0.15、0.97） were investigated by magnetic measurements.The values of M increase and exhibit weak irreversibility in the field-cooled (FC) magnetization curves. There are a clear bifurcation phenomenon of the field-cooled (MFC) and Zero-field-cooled (MZFC) magnetization curves.In the Molecule magnets Materials NBu4FeII0.10 MnII0.90[FeIII(OX)3],the Ne´el temperature is 34 K.And the Ne´el temperature of NBu4FeII0.15MnII0.85 [FeIII(OX)3] is 28 K.In the sample NBu4FeII0.03 MnII0.97[FeIII(OX)3],,the bifurcation of the ZFC and FC plots below the Ne´el temperature of 30 K indicates irreversibility.The oxalate group has been shown to be an excellent bridging ligand in supporting the magnetic exchange interaction.

Single-Crystal Magnetic Properties of [Co(NH3)5(OH2)] [Cr(CN)6] Between 2 and 300 K

1992 ◽  
Vol 45 (11) ◽  
pp. 1899 ◽  
Author(s):  
PA Reynolds ◽  
CD Delfs ◽  
BN Figgis ◽  
B Moubaraki ◽  
KS Murray
Keyword(s):  
Ising Model ◽  
Field Model ◽  
Mean Field ◽  
Zero Field ◽  
Spin Orbit Coupling ◽  
Zero Field Splitting ◽  
Magnetic Exchange Interaction ◽  
Mean Field Model ◽  
Magnetic Exchange ◽  
The Mean

The magnetic susceptibilities along and perpendicular to the c axis (hexagonal setting) between 2.0 and 300 K at a magnetic field of 1.00 T, and the magnetizations at field strengths up to 5.00 T, are presented for single crystals of [Co(NH3)5(OH2)] [Cr(CN)6]. The results are interpreted in terms of zero-field splitting (2D) of the ground 4A2g term by spin-orbit coupling and of magnetic exchange interaction between the chromium atoms. The magnetic exchange is modelled as one of Ising or mean-field in type. The exchange is found to be quite small: J = -0.18(6) cm-1 if the Ising model is employed, and -0.03(1) cm-1 for the mean-field model. The model adopted for the exchange has a strong influence on the value of the parameter D obtained. When the Ising model is used D is deduced to be -0.28(9) cm-l; when the mean-field model is used D is -0.14(4) cm-l. The g-values deduced are in agreement with those from e.s.r. measurements at higher temperatures and do not depend on the exchange model. In any case, D is found to be sufficiently large that it must be considered in a polarized neutron diffraction experiment on the compound.

Magnetic and Mössbauer Studies in Molecular-Based Magnets NBu4MAII[FeIII(OX)3](MA=Co, Fe)

2013 ◽  
Vol 538 ◽  
pp. 215-218
Author(s):  
Qing Lin ◽  
Qing Mei Zhang ◽  
Guo Dong Tang ◽  
Yun He ◽  
Xue Hui Long
Keyword(s):  
Phase Transition ◽  
Glass Phase ◽  
Magnetic Measurements ◽  
Magnetic Phase ◽  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Magnetic Pole ◽  
Mixed Valency ◽  
Mössbauer Studies ◽  
Spin Glass Phase

The mixed valency character and antiferromagnetic coupling in molecule magnets materials NBu4MAII[FeIII(OX)3]（MA=Co、Fe） were investigated by magnetic measurements and Mössbauer spectroscopy .In the sample NBu4CoII[FeIII(OX)3],the appearence of temperature point of spin-glass phase transition and magnetic phase transition under the zero-field-cooled AC magnetic measurements with the temperature range 5-100 K.The sample NBu4FeII[FeIII(OX)3] were carried out in the cooling modes in a field,and the sample exhibits multiple magnetic pole reversals in the warming mode magnetic measurements.The phenomenon of multiple magnetic pole reversals occurs in some of those ferrimagnetic materials consisting of magnetic anisotropy ions and two or more types of antiferromagnetically ordered magnetic ions.The compound NBu4FeII[FeIII(OX)3] contains two different spin carries; ie: Fe(II) (SFe(II)= 2), Fe(III) (SFe(III)= 5/2) comes from the Mössbauer studies.

Antiferromagnetism and metamagnetism in 1,4-diazine and pyridine complexes of nickel(II)

1995 ◽  
Vol 73 (2) ◽  
pp. 275-283 ◽  
Author(s):  
Tom Otieno ◽  
Robert C. Thompson
Keyword(s):  
Magnetic Properties ◽  
Electronic Spectroscopy ◽  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Critical Fields ◽  
Scanning Calorimetry ◽  
Magnetic Exchange ◽  
Nickel Ions ◽  
Pyridine Complexes

Several nickel(II) complexes containing pyridine (py), pyrazine (pyz) or methylpyrazine (mepyz) have been synthesized and characterized by vibrational and electronic spectroscopy, differential scanning calorimetry, and magnetic susceptibility studies to cryogenic temperatures. A comparison of the magnetic properties of the polymeric diazine-bridged complexes, Ni(pyz)2X2 (X = Cl or NO3), Ni(pyz)(p-CH3C6H4SO3)2, Ni(mepyz)(NO3)2, and Ni(pyz)3(CH3SO3)2•CH3OH with those of the related monometallic systems, Ni(py)4X2 (X = Cl, p-CH3C6H4SO3 or CH3SO3) and Ni(mepyz)4(NO3)2•H2O provides evidence for weak antiferromagnetic coupling between metal centers mediated by bridging diazine ligands in the former group of compounds. The magnetic properties were analyzed employing a model for S = 1 which takes into account zero-field splitting and employs a molecular field term to account for weak magnetic exchange. The compounds Ni(pyz)Cl2 and Ni(py)Cl2 show metamagnetic behaviour with critical fields of 13 and 2 kOe, respectively, at 2 K. In these compounds nickel ions, linked in chains by bridging chlorides, exhibit intrachain ferromagnetic and interchain antiferromagnetic exchange. In Ni(pyz)Cl2 bridging pyrazine ligands are considered to provide the pathway for the antiferromagnetic coupling resulting in a high critical field. Keywords: nickel(II), pyrazine, pyridine, complexes, metamagnetism, antiferromagnetism.

scholarly journals Complex magnetic properties associated with competing local and itinerant magnetism in $${\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mily Kundu ◽  
Santanu Pakhira ◽  
Renu Choudhary ◽  
Durga Paudyal ◽  
N. Lakshminarasimhan ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Neutron Diffraction ◽  
Single Phase ◽  
Magnetic Transition ◽  
Muon Spin Rotation ◽  
Antiferromagnetic Coupling ◽  
Diffraction Measurement ◽  
Zero Field ◽  
Crystalline Electric Field ◽  
X Ray

AbstractTernary intermetallic compound $${\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}$$ Pr 2 Co 0.86 Si 2.88 has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ($$\mu$$ μ SR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below $$\sim$$ ∼ 4 K. Neutron diffraction measurement further reveals that the magnetic ordering is antiferromagnetic in nature with an weak ordered moment. The high temperature magnetic phase has been attributed to glassy in nature consisting of ferromagnetic clusters of itinerant (3d) Co moments as evident by the development of internal field in zero-field $$\mu$$ μ SR below 50 K. The density-functional theory (DFT) calculations suggest that the low temperature magnetic transition is associated with antiferromagnetic coupling between Pr 4f and Co 3d spins. Pr moments show spin fluctuation along with unconventional orbital moment quenching due to crystal field. The evolution of the symmetry and the crystalline electric field environment of Pr-ions are also studied and compared theoretically between the elemental Pr and when it is coupled with other elements such as Co. The localized moment of Pr 4f and itinerant moment of Co 3d compete with each other below $$\sim$$ ∼ 20 K resulting in an unusual temperature dependence of magnetic coercivity in the system.

Synthesis of Iron Oxide Nanoparticles by Different Methods and Study of their Properties

2015 ◽  
Vol 230 ◽  
pp. 108-113 ◽  
Author(s):  
O.V. Yelenich ◽  
S.O. Solopan ◽  
T.V. Kolodiazhnyi ◽  
Jean Marc Greneche ◽  
Anatolii G. Belous
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Zero Field ◽  
X Ray Diffraction ◽  
Magnetic Studies ◽  
Brij 35 ◽  
Cryochemical Synthesis ◽  
Specific Loss Power ◽  
Triton X

In this work, iron oxide nanoparticles have been synthesized by precipitation in diethylene glycol, by cryochemical synthesis, in microemulsions using surfactants Triton X-100, Brij-35 and CTAB. Comparative spectroscopic, thermal, X-ray diffraction, 57Fe zero-field Mössbauer and magnetic studies of the synthesized nanoparticles have been carried out. Magnetic fluids prepared from synthesized nanopowders have been characterized by calorimetric measurements of specific loss power (SLP).

Interplay between spin crossover and exchange interaction in iron(III) complexes

2009 ◽  
Vol 81 (8) ◽  
pp. 1357-1383 ◽  
Author(s):  
Roman Boča ◽  
Ivan Nemec ◽  
Ivan Šalitroš ◽  
Ján Pavlik ◽  
Radovan Herchel ◽  
...  
Keyword(s):  
Experimental Data ◽  
Magnetic Susceptibility ◽  
Exchange Interaction ◽  
Spin Crossover ◽  
Magnetic Measurements ◽  
Spin States ◽  
Magnetic Exchange Interaction ◽  
Magnetic Exchange ◽  
Simultaneous Fitting ◽  
Polynuclear Metal Complexes

In the dinuclear and polynuclear metal complexes exhibiting the low-spin (LS) to high-spin (HS) transition, the spin-crossover phenomenon interferes with the magnetic exchange interaction. The latter manifests itself in forming spin-multiplets, which causes a possible overlap of the band originating in different reference spin states (LL, LH, HL, and HH). A series of dinuclear Fe(III) complexes has been prepared; the iron centers are linked by a bidentate bridge (CN-, and diamagnetic metallacyanates {Fe(CN)5(NO)}, {Ni(CN)4}, {Pt(CN)4}, and {Ag(CN)2}). Magnetic measurements confirm that the spin crossover proceeds on the thermal propagation. This information has been completed also by the Mössbauer spectral (MS) data. A theoretical model has been developed that allows a simultaneous fitting of all available experimental data (magnetic susceptibility, magnetization, HS mole fraction) on a common set of parameters.

scholarly journals Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

2020 ◽  
Vol 6 (4) ◽  
pp. 48
Author(s):  
Lu Xi ◽  
Jing Han ◽  
Xiaohui Huang ◽  
Licun Li
Keyword(s):  
Magnetic Properties ◽  
Magnetic Relaxation ◽  
Lanthanide Complexes ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Zero Field ◽  
Nitronyl Nitroxide ◽  
Ferromagnetic Exchange ◽  
Binuclear Structure ◽  
Slow Magnetic Relaxation

Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical while antiferromagnetic coupling dominates between two mono-radicals. Dynamic magnetic data show that the χ” signals of complex 3 exhibit frequency dependence under zero field, demonstrating slow magnetic relaxation behavior in complex 3. And the estimated values of Ueff and τ0 are about 8.4 K and 9.1 × 10−8 s, respectively.

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