A new method of the modifying factor for determining the broadband complex permeability of magnetic thin films,was proposed. Based on the measurement technology of shot-end microstrip line and the new modify factor,a series of FeCo-based magnetic thin films deposited on the oxidized silicon substrates and with an in-plane uniaxial anisotropy were measured in the frequency range of 0.5-5 GHz. The results fit well with the Landau-Lifchitz-Gilbert theory in a broad frequency range.
A single layer of CoFeB and a multilayer of CoFeB MgO films are prepared by means of DC/RF magnetron sputter deposition. The excellent microwave properties and high electrical resistivity are simultaneously achieved in the discontinuous multilayer structure of [Co44Fe44B12（0.7nm）/MgO（0.4nm）]40 film. This film has a high permeability （μ′） （larger than 100 below 2.1 GHz）, a high magnetic loss （μ″） （larger than 100 in a range from 1.5 to 3.3GHz）, a resistivity of 3.3 × 10^3μΩ. cm, a saturation magnetization of 1.2 T, and an in-plane uniaxial anisotropy field of 5.5 kA/m. The microstructure and the surface topography of the film are also analysed. The relatively large surface roughness for the discontinuous film is responsible for the wide frequency band of magnetic loss. The magnetic loss and the high resistivity indicate that the discontinuous CoFeB MgO multilayer film has potential applications in microwave absorbers and electromagnetic interference （EMI） shielding materials in a GHz frequency range.
An accurate theoretical study on the intrinsic point defects in rutile TiO2 was carried out by first-principles calculations using plane-wave pseudopotential method. The structural parameters of defect-free bulk rutile TiO2 were calculated,which are close to experimental data. And the effects of point defects on the geometry structures were analyzed. To get accurate value of formation energy and charge transfer levels,several technical details must be considered,such as the position of EVBM originating from supercell size and electrostatic interactions between the charged defects,and band-gap error etc. The formation energies of the point defects in various charge states were given as a function of Fermi level for the two limiting values of extreme O-rich conditions and extreme Ti-rich conditions. Under extreme Ti-rich conditions,Ti4+ interstitial and VO2+ have very low formation energy,and wound thus exist in significant quantities,namely,producing the intrinsic n-type TiO2. The stability of these point defects is traced back to the multivalence of titanium. Under extreme reducing condition,Frenkel defect comprised of Tii4+ and VTi4-would be formed in TiO2.
The nature of magnetic and electronic structure in double perovskite structure A2FeMoO6(A = Sr,a,Ca) was calculated using the local spin density approximation(LSDA) and the LSDA+U Coulomb interaction method of density functional theory. The result shows that Sr2FeMoO6 is magnetic metallic material,whereas Ba2FeMoO6 and Ca2FeMoO6 are half-metallic materials. Fe has great effect on the magnetic property of double perovskite structure A2FeMoO6 materials. Because of the orbit hybridization and polarization between the metal element and O element,the Mo element has magnetic properties. The static magnetic moment of double perovskite structure A2FeMoO6 materials,the value of the magnetic moment of these A2FeMoO6 for(A=Ca,Sr,Ba) are 3.626 43μB,2.678 64μB,3.706 17μB,respectively. The magnetic moment of Fe element in the crystal cell are,3.626 43μB,2.678 64 μB,3.706 17μB. And the energy of crystal cells are -28 540.561 907Ry,-24 268.037 272Ry,-44 106.187 179Ry. These values are in agreement with the experiment values.
