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Antiferromagnetically Coupled Binuclear Chromium(III) Complexes Through mi-Isophthalato-Bridge

100%

Li Y. , Yan C. W. , Guan H. S.

tom Vol. 77 / nr 8

953-959

Three new _-isophthalato-bridged binuclear chromium(III) complexes were synthesized and characterized, namely [Cr2(IPHTA)(Me2bpy)4](NO3)4 (1), [Cr2(IPHTA)(Me2phen)4](NO3)4 (2) and [Cr2(IPHTA)(Cl-phen)4](NO3)4 (3), where IPHTA represents the isophthalate dianions; Me2bpy, Me2phen and Cl-phen stand for 4,4_-dimethyl-2,2_-bipyridine; 2,9-dimethyl-1,10-phenanthroline and 5-chloro- 1,10-phenanthroline, respectively. The three complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, molar conductance and magnetic moments of room-temperature measurements, and spectroscopic studies, extended IPHTA-bridged structures consisting of two chromium( III) ions, each in an octahedral environment are proposed for these complexes. The complexes [Cr2(IPHTA)(Me2bpy)4](NO3)4 (1) and [Cr2(IPHTA)(Me2phen)4](NO3)4 (2) were further characterized by variable temperature magnetic susceptibility (4~300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, _ _ _ H JS S = Ĺ 2 1 2, giving the exchange integrals J = -1.27 cm-1 for (1) and J = -2.19 cm-1 for (2). This result indicates the presence of weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule.

Magnetic properties of mechanically milled nanosized Mn

100%

Wu X. J. , Xu X. W. , Sun X. S.

tom Vol. 27, No. 3

857--864

Nanosized Mn powders were fabricated by milling Mn flakes in pure ethyl alcohol followed by homogenization. XRD analysis confirms single-phase characterization of the product and shows it has a grain size of 40 nm. The ZFC and FC magnetizations exhibit a large irreversibility with onset of about 60 K. The fit of the Curie-Weiss relation indicates strong AFM interaction in the considered system. A large coercive field and shifted hysteresis loops, i.e. He = 83.6 kA/m, are observed at 5 K in the 2 T field cooling case. The analysis indicates that surface anisotropy can lead to the occurrence of large exchange bias.

Structure, magnetic and electrical transport properties of Mn4-xAgxN compounds

100%

Feng W. J. , Li D. , Zhang Q. , Deng Y. F. , Ma S. , Zhang Z. D.

tom Vol. 27, No. 1

33--42

Mn4-xAgxN compounds (x = 0.0, 0.3, 0.6, 1.0) were prepared by milling and subsequently annealing the mixture of Mn2N0.86, Mn, and Ag powders. All compounds display good single-phase characteristics. Both Mn4N and Mn3.7Ag0.3N exhibit ferrimagnetism, and a little Ag replacement of Mn can improve the saturation magnetization. The magnetic transition of Mn3.4Ag0.6N and Mn3AgN below 15 K is from triangular antiferromagnetism to non-coplanar ferrimagnetism, while the ones at 256 and 275 K (Mn3.4Ag0.6N and Mn3AgN, respectively) have been ascribed to the gradual transition, as temperature increases, from the triangular antiferromagnetic structure T5g to a ferrimagnetic-like one. Two minima appear on the p(T) curves for Mn3AgN, with the observation of a positive magnetoresistance throughout the whole tempeature-dependent change.

Nano-structured (Mo,Ti)C-C-Ni magnetic powder

51%

Kaczmarek S. M. , Biedunkiewicz A. , Bodziony T. , Figiel P. , Skibiński T. , Krawczyk M. , Gabriel-Półrolniczak U.

Journal of Achievements in Materials and Manufacturing Engineering

2018

tom Vol. 86, nr 1

5--13

Purpose: The paper presents the results of phase composition and magnetic properties of Mo-Ni-Ti-C nanostructured powders. The aim of this research is understanding the correlation between key magnetic properties and the parameters that influence them in the nanostructured powders from Mo-Ni-Ti-C system. Design/methodology/approach: The powder samples were synthesised using modified sol-gel method. Obtained powder were subjected for composition and magnetic properties in a wide temperature range by means of Electron Paramagnetic Resonance (EPR) and magnetic susceptibility measurements. To study the phase composition X-ray diffraction were performed. The morphology of the powders were investigated by scanning electron microscopy (SEM). Findings: Different kinds of structural and magnetic phases have been found in the investigated compounds, e.g. (Mo, Ti)C, C, Ni. It was found that such different phases create different kinds of magnetic interactions, from paramagnetic, antiferromagnetic up to superparamagnetic. Significant magnetic anisotropy has been revealed for low temperatures, which lowers with temperature increase. Moreover, non-usual increasing of the magnetization as a function of temperature was observed. It suggests, that overall longrange AFM interaction may be responsible for the magnetic properties. Research limitations/implications: For the future work explanation which phases in Mo-Ni-Ti-C system are responsible for different kinds of magnetic interactions are planned. Practical implications: The composition of different kinds of phases may be controlled to tune magnetic properties of the nanostructured Mo-Ni-Ti-C systems. Originality/value: In this study, for the first time Mo-Ni-Ti-C nanostructured samples were prepared with different kinds of structural and magnetic phases, creating different kinds of magnetic interactions, from paramagnetic, antiferromagnetic up to superparamagnetic-like. The latter seems to be formed due to the presence of magnetic nanoparticles and longrange antiferromagnetic interactions dominating in the whole temperature range.