Q.L. Liu

Effects of Cu on crystallographic and magnetic properties of Sm(Co,Cu)7

We have investigated the structural stability and magnetic properties of SMCo7-xCu, compounds with the TbCu7-type structure using x-ray powder diffraction and magnetic measurement. A large solid solution with 0.8 less than or equal to x less than or equal to 4.0 in SMCo7-xCux compounds has been observed. Both the lattice parameters and unit cell volume increase with increasing Cu content. SMCo7-xCux compounds exhibit ferromagnetic order. A strong uniaxial magnetocrystalline anisotropy with an anisotropy field as high as 20 T is obtained with x = 0.8 at 5 K. However, the saturation magnetization and Curie temperature decrease with increasing Cu content.

Crystal structure and magnetic properties of Gd3(Fe1-x-yCoyTix)29 compounds

A series of Gd-3(Fe1-x-yCoyTix)(29) (x = 0.011-0.034, y = 0-0.393) Samples have been prepared. Single-phase samples assigned as 3:29 compounds with the monoclinic lattice are obtained in the following composition regions: x; = 0.011, 0 less than or equal to y less than or equal to 0.307; x = 0.022, 0 less than or equal to y less than or equal to 0.313; and x = 0.034, 0 less than or equal to y less than or equal to 0.393. The solid-solution limit of cobalt in Gd-3(Fe1-x-yCOyTix)(29) increases with the Ti content. The cell parameters a, b and c show anisotropic decreases with the Co content, i.e. a and b decrease significantly and c decreases slightly in the composition range investigated. The Curie temperature is increased by the substitution of Co for Fe in Gd-3(Fe1-x-yCoyTx)(29). The saturation magnetization first increases and then decreases with the Co content. The dependence of the intrinsic magnetic properties of Gd-3(Fe1-x-yCoyTix)(29) on the Co and Ti contents is presented. The compounds exhibit an easy-magnetization direction on the a-b plane corresponding to the CaCu5-type structure at room temperature. The anisotropy field H-a of Gd-3(Fe1-x-yCoyTix)(29) is decreased and the magnetocrystalline anisotropy constant K-1 is increased by the substitution of Co for Fe. No spin reorientation is observed in the alternating-current susceptibility measurement between 77 K and the Curie temperature.

Subsolidus phase relations in the Co-rich region of the La–Co–Ti system

Subsolidus phase relations in the Go-rich region of the La-Go-Ti system have been investigated by means of X-ray diffraction. The phase diagram can be divided into six three-phase and three two-phase regions. In the investigated composition region, a new ternary compound exists: La2Co17-xTix (x=0.8-1.2) (Th2Zn17-type structure) (C) 2000 Elsevier Science S.A. All rights reserved.

A first principles study on optical transparency mechanism in Dy doped α-SiAlON ceramics

Dy doped α-SiAlON ceramics prepared by the hot-pressing method show a high optical transmittance value, >70%, in the infrared region of 1.5–4.5u2002μm. First principles calculations have been carried out to reveal the underlying transparency mechanism. It is found that the valence shell of doped Dy atoms interacts strongly with the doping states of α-SiAlON, resulting in the increase in the optical gap from 0.4 to 1.1 eV, which suppresses the photoabsorption in the wavelength region longer than 1.0u2002μm and leads to the good transparency property. The calculated optical transmission spectra are in good agreement with the corresponding experiments.

Formation of completely miscible solid-solution Gd5(Si1-xGex)4 induced by ferromagnetic exchange interaction

The crystal structure and magnetic properties of Gd-5(Si1-xGex)(4) compounds (0 less than or equal to x less than or equal to 1.0) are investigated by means of temperature dependent X-ray powder diffraction and magnetic measurements. A crystallographic and magnetic phase diagram of the pseudobinary system Gd5Si4-Gd5Ge4 is constructed. An intriguing observation is that Gd-5(Si1-xGex)(4) alloys form a completely miscible solid-solution at low temperature (< T-C), crystallizing in the Gd5Si4-type structure as indicated by the well-defined linear dependence of lattice parameters on germanium concentration x, and decomposing into three partially miscible solid-solutions above the Curie temperature, i.e. Gd5Si4 based (x < 0.5), Gd5Ge4 based (x greater than or equal to 0.8) and Gd5Si2Ge2 based (0.5 less than or equal to x < 0.8) solid-solutions, This unusual feature can be understood by taking into account competing effects of ferromagnetic exchange interaction and lattice strain in the solid-solution

Structure and magnetic properties of intermetallic compounds (La1−xRx)2Co16Ti (R=Sm, Nd)

The influence of R substitution in (La1-xRx)(2)Co16Ti compounds (R=Sm, Nd; x=0.0-1.0) on structural and magnetic properties has been investigated. The lattice parameters of the (La1-xRx)(2)Co16Ti compounds decrease with increasing x in the range 0 less than or equal to x less than or equal to 1.0. With x increasing, the saturation magnetic moment increases for (La1-xNdx)(2)Co16Ti while remains unaffected for (La1-xSmx)(2)Co16Ti. The Curie temperature increases with increasing Sm or Nd substitution. The uniaxial magnetocrystalline anisotropy of (La1-xSmx)(2)Co16Ti becomes enhanced with increasing Sm substitution. The anisotropy of (La1-xNdx)(2)Co16Ti changes from easy-axis (x 0.4)

Structure and magnetic properties of intermetallic compounds of the composition Gd3(Fe, Ni)28(Nb, Mo)

The effect of the substitution of Ni for Fe on the magnetic and structural properties of Gd-3(Fe28-xNix)(Nb1-y,Mo-y) (x less than or equal to 4, y=0.3 and 0.7) compounds have been studied. All of the compounds crystallize in the Nd3Fe29-xTix-type structure and the lattice parameters a, b, c and the unit cell volume V decrease with increasing Ni content. Substitution of Ni for Fe leads to a clear increase of the Curie temperature (T-C) and to a small decrease of the saturation magnetization (M-S). The compounds exhibit planar anisotropy perpendicular to the [102] direction. The anisotropy field H-A decreases with increasing Ni content. The effect of Ni substitution on the Curie temperature and the saturation magnetization are discussed

Structure and magnetic properties of intermetallic compounds (Gd1-xRx)3Fe28Nb (R = Ce, Nd, Sm)

The effect of the substitution of Sm, Nd and Ce for Gd on the structure and magnetic properties of (Gd1-x Rx )3 Fe28 Nb (R = Sm, Nd and Ce) compounds have been studied. The single-phase regions for R = Sm, Nd and Ce correspond to the composition range of 0 x 0.2, 0 x 0.5 and 0 x 0.4, respectively. All of the compounds crystallize in the Nd3 Fe29-x Tix -type structure. The lattice parameters a , b , c and V increase with the increase of the Sm and Nd content, while decrease with an increase of the Ce content. Substitution of Sm, Nd and Ce for Gd leads to a decrease of Curie temperature (TC ) and an increase of the saturation magnetization (MS ). The compounds (Gd1-x Smx )3 Fe28 Nb and (Gd1-x Ndx )3 Fe28 Nb exhibit planar anisotropy perpendicular to the [102] direction, the anisotropy field HA increases with the substitution content, while in compounds (Gd1-x Cex )3 Fe28 Nb, the planar anisotropy field HA decreases with an increase of the Ce content. (Gd0.6 Ce0.4 )3 Fe28 Nb exhibits an intermediate easy axis behaviour.

Study on the Preparation and Properties of Colored Iron Oxide Thin Films

Colored iron oxide thin films were prepared using Sol-gel technique. The raw materials were tetraethyl orthosilicate (TEOS), etoh ehanol (EtOH), iron nitrate, and de-ionized water. Various properties were measured and analysed, including the colour of thin films, surface topography, UV-Visible spectra, corrosion resistance and hydrophobicity. To understand how these properties influenced the structural and optical properties of Fe2O3 thin films, Scanning Electron Microscope (SEM), UV Spectrophotometer and other facilities were employed. Many parameters influence the performance of thin films, such as film layers, added H2O content, and the amount of polydimethylsiloxane (PDMS). When the volume ratio of TEOS, EtOH and H2O was 15: 13: 1, the quality of Fe(NO3)3·9H2O was 6g, and pH value was 3, reddish and uniform Fe2O3 thin films with excellent properties were produced. Obtained thin films possessed corrosion resistance in hydrochloric acid with pH=l and the absorption edge wavelength was ~350.2nm. Different H2O contents could result in different morphologies of Fe2O3 nanoparticles. When 1.5 ml PDMS was added into the Sol, thin films possessed hydrophobiliry without dropping. Coating with different layers, thin films appeared different morphologies. Meanwhile, with the increment of film layers, the absorbance increased gradually.

Structure and magnetic properties of intermetallic compounds Gd3(Fe,Nb)29

The crystal structure and magnetic properties of intermetallic Gd3Fe29−xNbx compounds (0.9⩽x⩽1.3) have been investigated by x-ray powder diffraction and magnetic measurement. The lattice parameters of Gd3Fe29−xNbx with the Nd3Fe29−xTix-type structure are a=10.606–10.618u200aA, b=8.529–8.552u200aA, c=9.703–9.711u200aA, and β=96.962–96.944°: Nb atoms show a strong preference to occupy 4g, 4i3, and 4i4 crystallographic positions. The Nb content dependence of the Curie temperature exhibits a maximum value of Tcmax=516u200aK when x=1.2. The saturation magnetization Ms linearly decreases with increasing Nb content at 1.5 K, from 36.39u200aμB/f.u. to 35.30u200aμB/f.u. The compound exhibits a planar anisotropy perpendicular to the [102] direction. The anisotropy field HA also linearly decreases with increasing Nb content at 1.5 K, from 6.9 to 5.0 T. In contrast to other Nd3Fe29−xTix-type iron-rich compounds, Gd3Fe29−xNbx compounds have higher Curie temperature, higher saturation magnetization, and room-temperature stability.