Novel Insights in the Magnetic Behavior of Non-Stoichiometric LaMnO3+δ Nanoparticles

2021 ◽  
Author(s):  
José M González-Calbet ◽  
Antonio Hernando ◽  
Jose Alonso ◽  
Kevin M. Sigcho ◽  
Alberto Azor-Lafarga ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Exchange Interactions ◽  
Magnetic Behavior ◽  
Antiferromagnetic Ordering ◽  
Reactivity Of Solids ◽  
Material Sciences

LaMnO3+δ is one of the classical-formal nonstoichiometric systems in Material Sciences that, for δ=0, shows antiferromagnetic ordering by super-exchange interactions between Mn3+ ions. Nevertheless, the chemical reactivity of solids goes...

Rb2CaCu6(PO4)4O2, a novel oxophosphate with a shchurovskyite-type topology: synthesis, structure, magnetic properties and crystal chemistry of rubidium copper phosphates

2019 ◽  
Vol 75 (5) ◽  
pp. 903-913
Author(s):  
Sergey M. Aksenov ◽  
Elena Yu. Borovikova ◽  
Vladimir S. Mironov ◽  
Natalia A. Yamnova ◽  
Anatoly S. Volkov ◽  
...  
Keyword(s):  
Multicomponent System ◽  
Exchange Interactions ◽  
Magnetic Behavior ◽  
Molar Ratio ◽  
Monoclinic Space Group ◽  
Antiferromagnetic Exchange ◽  
X Ray ◽  
Low Dimensional ◽  
Fierce Competition ◽  
Ordered State

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

Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages

2015 ◽  
Vol 4 (6) ◽  
Author(s):  
Athanasia Kostopoulou ◽  
Alexandros Lappas
Keyword(s):  
Magnetic Particles ◽  
Critical Role ◽  
Exchange Interactions ◽  
Magnetic Behavior ◽  
Building Blocks ◽  
Spatial Arrangement ◽  
Magnetic Characteristics ◽  
Surface Functionality ◽  
Magnetic Nanocrystal

AbstractMagnetic particles of optimized nanoscale dimensions can be utilized as building blocks to generate colloidal nanocrystal assemblies with controlled size, well-defined morphology, and tailored properties. Recent advances in the state-of-the-art surfactant-assisted approaches for the directed aggregation of inorganic nanocrystals into cluster-like entities are discussed, and the synthesis parameters that determine their geometrical arrangement are highlighted. This review pays attention to the enhanced physical properties of iron oxide nanoclusters, while it also points to their emerging collective magnetic response. The current progress in experiment and theory for evaluating the strength and the role of intra- and inter-cluster interactions is analyzed in view of the spatial arrangement of the component nanocrystals. Numerous approaches have been proposed for the critical role of dipole-dipole and exchange interactions in establishing the nature of the nanoclusters’ cooperative magnetic behavior (be it ferromagnetic or spin-glass like). Finally, we point out why the purposeful engineering of the nanoclusters’ magnetic characteristics, including their surface functionality, may facilitate their use in diverse technological sectors ranging from nanomedicine and photonics to catalysis.

THE MAGNETIC BEHAVIOR OF (Y1-xTbx)3Co11B4 INTERMETALLIC COMPOUNDS

1999 ◽  
Vol 13 (25) ◽  
pp. 905-910
Author(s):  
R. TETEAN ◽  
V. POP ◽  
E. BURZO ◽  
I. GR. DEAC
Keyword(s):  
Magnetic Properties ◽  
Intermetallic Compounds ◽  
Exchange Interactions ◽  
Magnetic Behavior ◽  
Hexagonal Structure ◽  
External Fields ◽  
Space Group ◽  
Temperature Range ◽  
Ferrimagnetic Ordering ◽  
Curie Temperatures

The R 3 Co 11 B 4 compounds belong to the R n+1 Co 3n+5 B 2n intermetallic systems. The R 3 Co 11 B 4 borides crystallize in a hexagonal structure of Ce 3 Co 11 B 4 type having the space group P6/mmm. The composition dependencies of the lattice parameters in ( Y 1-x Tb x)3 Co 11 B 4 compounds are linear and different for a and c parameters. The magnetic properties of ( Y 1-x Tb x)3 Co 11 B 4 compounds were investigated in the temperature range 4.2–950 K and external fields up to 10 T. The Y 3 Co 11 B 4 compound is ferromagnetically ordered. For the compounds with x>0, a ferrimagnetic ordering is evidenced. The Curie temperatures increase when yttrium is substituted by terbium, as a consequence of the increase of the exchange interactions in the system. The magnetic behavior of cobalt in the above system is analyzed.

Dislocations and the thermal reactivity of calcite

1970 ◽  
Vol 314 (1518) ◽  
pp. 429-441 ◽  
Keyword(s):  
Chemical Reactivity ◽  
Previous History ◽  
Strain Fields ◽  
Temperature Range ◽  
Reactivity Of Solids ◽  
Dislocation Movement ◽  
History Of ◽  
First Time ◽  
Kinetics Of

A study has been made of the effect of dislocation movement on the kinetics of thermal decomposition of freshly cleaved calcite crystals. It is shown for the first time that the thermal history of the crystal has a marked effect on its reactivity and two patterns of behaviour have been identified; that in the temperature range up to ca . 700 K in which the kinetics of decomposition are sensitively dependent upon the nature and extent of the crystal’s previous history, and the range above 700 K in which annealing is rapid and reproducible kinetics are obtained for all crystals studied. This effect has not been observed in previous studies of calcite. It is suggested that this is because the experiments were carried out in the temperature range where movement of dislocations is so rapid that the surface structure is virtually constant during the measurements. Tentative correlations are made between the various stages of the observed rates of decomposition and the known dislocation systems in the crystal. The influence of applied stress was studied but because of limitations in the method of stressing the crystal, the amount of plastic deformation was small and its effect on reactivity was not marked. Qualitative consideration is given to the role of dislocations in the reactivity of solids and it is concluded that the elastic energy associated with the strain fields around or at the core of the dislocation cannot be used to promote chemical reactivity but that it is the change in the stereochemical environment of molecules in the dislocated region of the crystal which is important. ‘ . . . a curious illustration of the influence of mechanical forces over chemical affinity. . . ’ M. Faraday (1834)

Magnetic behaviour of synthetic Co2SiO4

2009 ◽  
Vol 65 (6) ◽  
pp. 664-675 ◽  
Author(s):  
Andrew Sazonov ◽  
Martin Meven ◽  
Vladimir Hutanu ◽  
Gernot Heger ◽  
Thomas Hansen ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moment ◽  
Mirror Symmetry ◽  
Magnetic Moments ◽  
Exchange Interactions ◽  
Magnetic Behaviour ◽  
Relative Strength ◽  
Antiferromagnetic Ordering ◽  
Polarized Neutron

Synthetic Co2SiO4 crystallizes in the olivine structure (space group Pnma) with two crystallographically non-equivalent Co positions and shows antiferromagnetic ordering below 50 K. We have investigated the temperature variation of the Co2SiO4 magnetic structure by means of non-polarized and polarized neutron diffraction for single crystals. Measurements with non-polarized neutrons were made at 2.5 K (below T N), whereas polarized neutron diffraction experiments were carried out at 70 and 150 K (above T N) in an external magnetic field of 7 T parallel to the b axis. Additional accurate non-polarized powder diffraction studies were performed in a broad temperature range from 5 to 500 K with small temperature increments. Detailed symmetry analysis of the Co2SiO4 magnetic structure shows that it corresponds to the magnetic (Shubnikov) group Pnma, which allows the antiferromagnetic configuration (Gx , Cy , Az ) for the 4a site with inversion symmetry \bar{1} (Co1 position) and (0,Cy ,0) for the 4c site with mirror symmetry m (Co2 position). The temperature dependence of the Co1 and Co2 magnetic moments obtained from neutron diffraction experiments was fitted in a modified molecular-field model. The polarized neutron study of the magnetization induced by an applied field shows a non-negligible amount of magnetic moment on the oxygen positions, indicating a delocalization of the magnetic moment from Co towards neighbouring O owing to superexchange coupling. The relative strength of the exchange interactions is discussed based on the non-polarized and polarized neutron data.

Synthesis and Surface Engineering of La1-xSrxMO3 Nanoparticles for Biomedical Applications

2014 ◽  
Vol 1081 ◽  
pp. 171-174
Author(s):  
Wen Zheng Cheng ◽  
Wu Zhang ◽  
Hong Ling Liu ◽  
Xue Mei Li ◽  
Xiao Liu
Keyword(s):  
Surface Modification ◽  
Electrical Properties ◽  
Biomedical Applications ◽  
Surface Engineering ◽  
Chemical Reactivity ◽  
Magnetic Hyperthermia ◽  
Review Article ◽  
Hyperthermia Treatment ◽  
Material Sciences ◽  
Curie Temperature Tc

La1-xSrxMO3 nanoparticles have attracted increasing interest to material sciences due to their tunable Curie temperature (Tc), superparamagnetic nature and electrical properties, which could be utilized in magnetic hyperthermia treatment. However, La1-xSrxMO3 nanoparticles are toxity to biomolecules and very sensitive to oxidation because of their higher chemical reactivity. The surface modification could enhance stability, dispersibility and compatibility of La1-xSrxMO3 nanoparticles. This review article will introduce the progress on the synthesis and surface modification of La1-xSrxMO3 nanoparticles in recent years, and then give the perspectives of outlook.

scholarly journals Magnetic behavior of Fe-doped of multicomponent bismuth niobate pyrochlore

2021 ◽  
Vol 60 (1) ◽  
pp. 38-46
Author(s):  
Nadezhda A. Zhuk ◽  
Boris A. Makeev ◽  
Sergey V. Nekipelov ◽  
Maria V. Yermolina ◽  
Anna V. Fedorova ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Solid Phase ◽  
Synthesis Method ◽  
Pyrochlore Structure ◽  
Exchange Interactions ◽  
Magnetic Behavior ◽  
Susceptibility Data ◽  
Nexafs Spectroscopy ◽  
Magnetic Dilution ◽  
Paramagnetic Atoms

Abstract Two series of iron-containing solid solutions Bi2Mg1− x Fe x Nb2O9+δ and Bi2MgNb2−2 x Fe2 x O9−δ of pyrochlore structure were obtained by the traditional solid phase synthesis method. The electronic state and character of exchange interactions of iron atoms in solid solutions were investigated by methods of magnetic dilution and NEXAFS-spectroscopy. According to X-ray spectroscopy and magnetic susceptibility data, iron(III) atoms are distributed mainly in octahedral positions of niobium(V) and in a dominant amount are in the charge state of Fe(III) in the form of monomers and exchange-bonded clusters mainly with antiferromagnetic type of exchange. Differences in magnetic behavior of iron-containing solid solutions of both series have been revealed. Antiferromagnetic and ferromagnetic exchange can be realized between iron atoms, which, with increasing concentration of paramagnetic atoms and averaging structure distortions, becomes less significant. The parameters of exchange interactions in clusters and distribution of iron paramagnetic atoms depending on the concentration of solid solutions have been calculated.

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