Effects of Heating Processing on Microstructure and Magnetic Properties of Mn-Zn Ferrites Prepared via Chemical Co-precipitation

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）, frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel MnxZn1-xfe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 ℃, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 ℃ is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

Density Functional Theory Study on Electronic and Magnetic Properties of Mn-doped （MgO）n （n=2-10） Clusters

We study the geometries, stabilities, electronic and magnetic properties of （MgO）n （n=2-10） clusters doped with a single Mn atom using the density functional theory with the gener- alized gradient approximation. The optimized geometries show that the impurity Mn atom prefers to replace the Mg atom which has low coordination number in all the lowest-energy MnMgn-1On （n=2-10） structures. The stability analysis clearly represents that the average binding energies of the doped clusters are larger than those of the corresponding pure （MgO）n clusters. Maximum peaks of the second order energy differences are observed for MnMg~_1On clusters at n=6, 9, implying that these clusters exhibit higher stability than their neighboring clusters. In addition, all the Mn-doped Mg clusters exhibit high total magnetic moments with the exception of MnMgO2 which has 3.00μB. Their magnetic behavior is attributed to the impurity Mn atom, the charge transfer modes, and the size of MnMgn- 1On clusters.

Effect of Sm-doping on the morphology and magnetic properties of radio frequency magnetron sputtered Ni-Mn-Ga films

Ni55.5Mn21Ga23.5 and Ni54Mn22Ga23Sml films were prepared by radio frequency （RF） magnetron sputtering. The effect of Sm do- pant on the morphologic and magnetic properties of Ni55.5Mn21Ga23.5 films was investigated. Sm doping can refine the particle size of the films from 100 to 60 nm, and further grain growth is not occurs even after annealing at 1073 K for 3.6 ks. Compared to Ni55.5Mn21Ga23.5 films, Sm-doped Ni54Mn22Ga23Sml films are easier to be magnetized and have a lower martensitic transformation temperature. In addition, the Curie temperature can also be adjusted, decreasing from 350 to 325 K after Sm doping. Martensitic transformation is not observed in the Sm-free films, which is close to the Curie temperature in the Sm-doped films, giving rise to the overlap of the structural and magnetic transi- tion temperatures.

Electronic and magnetic properties at rough alloyed interfaces of Fe/Co on Au substrates: An augmented space study

We studied the interface electronic and magnetic properties of Fe/Co deposited on Au substrate and researched the effects of roughness at the interfaces within augmented space formalism （ASF）. The full calculation is carried out by recursion and tight-binding linear muffin tin orbital （TB-LMTO） methods. The amount of roughness is different at different atomic layers. The formalism is also applied to sharp interface, when interdiffusion of atoms is negligible. Our results of one monolayer transition metal agree with other reported results. A realistic rough interface is also modeled with three and four monolayers of transition metals, deposited on Au substrates.

Structural evolutions and electronic properties of Au_nGd(n=6–15)small clusters:A first principles study

Structural, electronic, and magnetic properties of AunGd （n = 6-15） small clusters are investigated by using first principles spin polarized calculations and combining with the ab-initio evolutionary structure simulations. The calculated binding energies indicate that after doping a Gd atom AunGd cluster is obviously more stable than a pure AUn＋l cluster. Au6Gd with the quasiplanar structure has a largest magnetic moment of 7.421 gB. The Gd-4f electrons play an important role in determining the high magnetic moments of AunGd clusters, but in Au6Gd and Aul2Gd clusters the unignorable spin polarized effects from the Au-6s and Au-5d electrons further enhance their magnetism. The HOMO-LUMO （here, HOMO and LUMO stand for the highest occupied molecular orbital, and the lowest unoccupied molecular orbital, respectively） energy gaps of munGd clusters are smaller than those of pure AUn＋l clusters, indicating that AunGd clusters have potential as new catalysts with enhanced reactivity.

Structural and Magnetic Properties of Chemically Synthesized Pd-Modified NiFe2O4 Nanoparticles

Magnetic nanoparticles of NiFe2O4-Pd composites have been synthesized using a simple, low cost, sol-gel auto-combustion method. As-prepared samples were sintered at 800℃ for 6 h in order to develop the crystalline phase. X-ray diffraction confirmed the spinel structure of the ferrite samples. Structural morphology and size of the nanoparticles were evaluated using a field emission scanning electron microscope. Magnetic hysteresis loops were obtained at 300 and 100 K using a physical properties measurement system. The value of saturation magnetization was observed to decrease at the temperatures with the increase of Pd contents up to 5% but then a sudden rise in saturation magnetization was observed for the addition of 10% Pd in NiFe2O4.

Efects of Molybdenum Concentration and Valence State on the Structural and Magnetic Properties of BaFe_(11.6)Mo_xZn_(0.4-x)O_(19) Hexaferrites

Barium hexaferrites BaFe11.6Mox Zn0.4-x O19（x=0.1,0.2,0.4）were prepared by precipitation of the precursors using wet chemical mixture method and then sintering the dried powders at 1100℃.The properties of the prepared samples were investigated using X-ray difraction（XRD）,scanning electron microscopy（SEM）,vibrating sample magnetometer,and Mssbauer spectroscopy.XRD patterns revealed that all prepared samples had BaFe12O19hexaferrite structure as a majority phase.SEM images demonstated that the samples consisted mainly of hexagonal platelet-like grains with diameters ranging from 100 to 500 nm.Mssbauer spectra revealed that Zn2＋ions occupy 4f1 sites leading to the splitting of the 12k component.However Mo6＋ions occupy 2b sites while Mo4＋ prefer 4f1 and 12k sites.For the sample with x=0.4,Mo6＋and Mo4＋ ions were found to have preference for 2b and 12k sites,respectively,and to induce the development of Fe2＋ions in the hexaferrite,leading to noticeable changes in the magnetic properties of the system.The observed magnetic properties were found to be consistent with the preferential site occupation of metal ions,and the hyperfine fields derived from Mssbauer spectra of these samples.

Electronic transport and magnetic performance of Ni-Nb-Zr metallic glasses

The electronic transport and magnetic perfor- mances of Ni-Nb-Zr metallic glasses under low temperature were investigated. X-ray diffraction （XRD） analysis indicates that the Ni-Nb-Zr ribbons prepared by induction melting and melt spinning method have single amorphous phase. The electrical transport property results of these metallic glass alloys indicate that the Ni-Nb-Zr metallic glasses have negative resistivity temperature coefficients （RTC） and low- temperature drift. The negative RTC and corresponding pos- sible values of Fermi energy of Ni-Nb-Zr metallic glasses are interpreted by the extended Ziman-Faber diffraction theory. The magnetic measurements indicate that the magnetic in- tensities of the Ni-Nb-Zr metallic glasses are related to Ni content and atomic sizes while the low temperature has few influences on the magnetic properties.