(3,3)-Connected Three-dimentional Supramolecular Metal Organic Polyhedral Based on Nanometresized Ligand with Magnetism Properties

A three-dimentinal metal organic framework[Co₂(L)Cl(DMF)₂(H₂O)](DMF)₃(H₂O)₃ based on the nanometresized ligand 4,4',4"-[1,3,5-benzenetriyltris(carbonylimino)]trisbenzoic acid was synthesized, and characterized by means of single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetry analysis and magnetism. This obtained structure can be considered to be constructed from 2D layer, which displays the topology of hbc based on Co₂(COO)₃ secondary building unit, and further to be linked into a 3D supramolecular architecture by N-H…O hydrogen bonds. The magnetism of the complex was carried out, which shows ferromagnetic exchange interactions.     

Thin films of semiconducting lithium ferrite produced by pulsed laser deposition

Thin films of lithium ferrite (Li_0.5Fe_2.5O₄) have been deposited on (0 0 1) Al₂O₃ by pulsed laser deposition, with substrate deposition temperatures ranging between 500 and 800 °C, and oxygen pressures between 1 × 10⁻¹ and 4 × 10⁻⁷ mbar. X-ray diffraction shows that films grow with a (1 1 1) orientation. Conversion electron Mössbauer spectra for the high-pressure films show a single sextet with a hyperfine field of 49 T, while the low-pressure films show two sextets with hyperfine fields of 47 and 49 T. The spectra also reveal paramagnetic ferric iron in both types of films. Magnetization measurements of the films show a saturation magnetization of between 1.7 and 3.1μ_B per formula unit and a coercivity of between 10 and 44 mT. The films prepared under the lower oxygen pressures are semiconducting with resistivities of 2 × 10⁻² to 8 × 10⁻² Ω cm. They exhibit an anomalous Hall effect with p-type conduction at 175 K.     

Magnetic properties of (Ce1−xLax)PdIn2

We report on results of X-ray powder diffraction, magnetization and specific heat measurements of the pseudo-ternary (Ce_1−xLa_x)PdIn₂ system with x=0; 0.2; 0.4 and 0.6. The results show a linear increase of the unit cell volume and a reduction of the ferromagnetic transition as La content increases. The Debye temperature, Sommerfeld coefficient and crystal field parameters were estimated from specific heat data, and are found to be weakly dependent of the Ce concentration. Also, the variation of magnetic entropy at T_C is only weakly dependent on x (ΔS≅0.92Rln2) indicating that T_K/T_C is approximately constant along the series. The T_C and T_K behaviors are explained by the variation of the exchange parameter due to the volume change when Ce is replaced by La. Our results indicate that the chemical pressure is the dominant effect rather than the chemical disorder for determining the physical proprieties of the (Ce_1−xLa_x)PdIn₂ system.     

Experimental determination technique for magnetic anisotropy of individual nanowires

We present an experimental technique to determine the magnetic anisotropy of ferromagnetic nanowires. In the technique, the magnetization state is monitored by measuring the anisotropic magnetoresistance with rotating the external magnetic field. The measured magnetoresistance curves exhibit basically the same curves typically appeared in the torque magnetometric measurements, which are then readily analyzed based on the Stoner–Wohlfarth theory with a single fitting parameter – the magnetic anisotropy. By applying the present technique to Permalloy nanowires, it is shown that the shape anisotropy in real nanowires is significantly influenced by the edge roughness.     

Composition, structure and magnetic properties of sputter deposited Ni-Mn-Ga ferromagnetic shape memory thin films

Polycrystalline Ni-Mn-Ga thin films were deposited by the d.c. magnetron sputtering on well-cleaned substrates of Si(1 0 0) and glass at a constant sputtering power of 36 W. We report the influence of sputtering pressure on the composition, structure and magnetic properties of the sputtered thin films. These films display ferromagnetic behaviour only after annealing at an elevated temperature and a maximum saturation magnetization of 335 emu/cc was obtained for the films investigated. Evolution of martensitic microstructure was observed in the annealed thin films with the increase of sputtering pressure. The thermo-magnetic curves exhibited only magnetic transition in the temperature range of 339-374 K. The thin film deposited at high sputtering pressure of 0.025 mbar was found to be ordered L2₁ austenitic phase.     

Structural and magnetic properties of ferromagnetic In1−xMnxAs1−yPy layers

The structural and magnetic properties of epitaxial In_1−xMn_xAs_1−yP_y quaternary layers with Mn content ranging from 0.01 to 0.04 and phosphorous content ranging from 0.11 to 0.21 were studied. X-ray diffraction indicated that the films were two phase consisting of an InMnAsP solid solution and hexagonal MnAs nanoprecipitates. Addition of phosphorus promoted precipitate formation. Films were ferromagnetic showing hysteretic behavior in the field dependence of magnetization at 5 and 298 K. From field-cooled magnetization measurements ferromagnetic transitions were observed at 280 and 325 K. The zero field-cooled magnetization versus temperature measurements showed irreversibility for T<300 K that was attributed to the presence of MnAs nanoprecipitates. The calculated coercivity using the Neel model was 1380 G compared to the experimental value of 380 G at 5 K. The difference was attributed to a strong inter-cluster exchange that stabilizes the ferromagnetic state.     

Core-shell structured iron nanoparticles well dispersed on montmorillonite

Iron nanoparticles have been successfully synthesized using sodium borohydride solution reduction of ferric trichloride hexahydrate in the presence of montmorillonite as an effective protective reagent and support as well. A combination of characterizations reveals the well disperse of these obtained iron nanoparticles supported on the external surface of clay with roughly spherical morphology and mean diameter of 55 nm. The particles are oxidation resistant well with iron core-iron oxide shell structure. The shell thickness of 3 nm remains almost invariable under ambient conditions. Discernable hysteresis loop reveals ferromagnetic behavior of the iron nanoparticles, which make them easy for magnetic separation and potential in some practical applications.     

Damping and modal structure of patterned magnetic nanoarrays

A number of studies have shown that ferromagnetic resonance linewidths in magnetic thin films contain a significant contribution due to processes, such as inhomogeneous broadening and two-magnon scattering followed by decay to the phonon thermal bath. We present a classical theoretical approach that permits the calculation of such processes for arrays of arbitrarily shaped magnetic nanoparticles and, by comparison with experimental results, demonstrates that the linewidth broadening and damping are dominated by inhomogenities that strongly depend on the equilibrium state of magnetization and can be used to identify the latter.     

链式钴微米六方片的溶剂热合成及磁性

以十二硫醇和聚乙烯吡咯烷酮（PVP）为结构导向剂、乙二醇和乙二胺为混合溶剂,利用溶剂热技术成功地制备了Co粒子,并用XRD、SEM、TEM、HRTEM及SQUID对材料的晶体结构、形貌及磁性进行研究. 结果表明：Co粒子属hcp相,呈六方片状,直径约为2 μm,厚度约为80 nm,大量的六方片相互交叉连接成链式结构,并且六方薄片由更为细小的丝带状的纳米片（厚度约为10 nm）构成;室温下样品表现出良好的铁磁性特征,其饱和磁化强度Ms、剩余磁化强度Mr及矫顽力分别为126.6 emu/g、13.7 emu/g和163.4 Oe.