Morphology and magnetic properties of Co0.8Fe2.2O4 films prepared by the chemical solution deposition

Co_0.8Fe_2.2O₄ ferrite thin films have been prepared on Si(0 0 1) substrates by the chemical solution deposition. Structural characteristics indicate all films are single phase with spinel structure and the space group and the mean grain size increases from 8 to 30 nm with the increase of annealing temperature. The magnetic properties of Co_0.8Fe_2.2O₄ thin films are highly dependent on annealing temperature. The sample annealed at 800 °C possesses high saturation magnetization, moderate coercivity and squareness ratio, making it a promising application candidate in high-density record and magneto-optical materials.     

Hyperfine interaction in Co2SiO4 investigated by high resolution neutron spectroscopy

We have investigated the hyperfine interaction in Co₂SiO₄ by inelastic neutron scattering with a high resolution back-scattering neutron spectrometer. The energy spectrum measured from a Co₂SiO₄ powder sample revealed inelastic peaks at at T=3.5 K on both energy gain and energy loss sides. The inelastic peaks move gradually towards lower energy with increasing temperature and finally merge with the elastic peak at the electronic magnetic ordering temperature . The inelastic peaks have been interpreted to be due to the transition between hyperfine-split nuclear level of the ⁵⁹Co isotopes with spin . The temperature dependence of the energy of the inelastic peak in Co₂SiO₄ showed that this energy can be considered to be the order parameter of the antiferromagnetic phase transition. The determined hyperfine splitting in Co₂SiO₄ deviates from the linear relationship between the ordered electronic magnetic moment and the hyperfine splitting in Co, Co-P amorphous alloys and CoO presumably due to the presence of unquenched orbital moment. These results are very similar to those of CoF₂ recently reported by Chatterji and Schneider [7].     

The high quality ZnO growth on c-Al2O3 substrate with Cr2O3 buffer layer using plasma-assisted molecular beam epitaxy

High quality epitaxial ZnO films were grown on c-Al₂O₃ substrates with Cr₂O₃ buffer layer by plasma-assisted molecular beam epitaxy (P-MBE). The hexagonal crystalline Cr₂O₃ layer was formed by oxidation of the Cr-metal layer deposited on the c-Al₂O₃ substrate using oxygen plasma. The epitaxial relationship was determined to be ZnO//Cr₂O₃//Cr//Al₂O₃ and ZnO//Cr₂O₃//[0 0 1]Cr//Al₂O_3. The Cr₂O₃ buffer layer was very effective in improving the surface morphology and crystal quality of the ZnO films. The photoluminescence spectrum showed the strong near band-edge emissions with the weak deep-level emission, which implies high optical quality of the ZnO films grown on the Cr₂O₃ buffer.     

Magnetic susceptibility of vanadium garnets NaPb2Co2V3O12 and NaPb2Ni2V3O12

Vanadium garnets NaPb₂Co₂V₃O₁₂ and NaPb₂Ni₂V₃O₁₂ have been successfully synthesized. The X-ray diffraction experiments indicate that these compounds have the garnet structure of cubic symmetry of space group with the lattice constant of 12.742 Å (NaPb₂Co₂V₃O₁₂) and 12.666 Å (NaPb₂Ni₂V₃O₁₂), respectively. The magnetic susceptibility of NaPb₂Ni₂V₃O₁₂ shows the Curie-Weiss paramagnetic behavior between 4.2 and 350 K. The effective magnetic moment μ_eff of NaPb₂Ni₂V₃O₁₂ is 3.14 μ_B due to Ni²⁺ ion at A-site and the Weiss constant is −3.67 K (antiferromagnetic sign). For NaPb₂Co₂V₃O₁₂, the simple Curie-Weiss law cannot be applicable. The ground state is the spin doublet and the first excited state is spin quartet , according to Tanabe-Sugano energy diagram on the basis of octahedral crystalline symmetry. This excited spin quartet state just a bit higher than ground state influences strongly the complex temperature dependence of magnetic susceptibility for NaPb₂Co₂V₃O₁₂.     

Nanostructure and excellent magnetic properties of Co19.35Fe53.28Hf7.92O19.35 films

This letter reports the novel nanostructure and excellent magnetic properties of Co_19.35Fe_53.28Hf_7.92O_19.35 films with varying thicknesses. Among the samples investigated, the film with a thickness of 432 nm exhibits the most excellent magnetic properties: high saturation magnetization, , low coercivity, , and high hard-axis anisotropy field of . The magnetic permeability remains almost stable up to 3 GHz and reaches a maximum at the ferromagnetic resonant frequency of 4.024 GHz. The excellent magnetic characteristics of this film in addition to a very high electrical resistivity of 3569 μΩ cm make it ideal for uses in high-frequency applications of micromagnetic devices. It reveals that these superior properties are ascribed to the formed peculiar nanostructure. A magnetic phase separation appears to occur strongly as the film thickness increases over 437 nm, which, in turn, modifies the high-frequency behavior.     

Surface assisted electric transport in Ag2S thin films

Electric transport measurements of thickness-dependent electronic and ionic conductivity of epitaxial Ag₂S films are used to split both kinds of conductivity into bulk and surface components. The established considerable electronic and ionic surface conductances demonstrate unambiguously the co-existance of electronic and ionic space charge regions in the vicinity of silver sulfide free surface oriented along the zone axes []. The parameters of both space charge layers - surface potential, thickness of the space charge region and concentration of the surface compensating charges, are calculated. It is estimated that for intrinsic silver sulfide, the effective surface potential of () Ag₂S surface is negative, its value being about −610 mV at 400 K.