Zun-Xiao Liu

Magnetic properties of

and samples were prepared by arc melting and then annealed in vacuum. For the Nd-rich samples, type structure was obtained by a long annealing (, 48 d); for the Sm-rich samples, it was obtained by a short annealing (750 - , 1 d). With increasing Sm content, the easy magnetization direction converts from the basal plane to the c-axis. An easy-c-axis anisotropy is observed at room temperature for . A small amount of Ti favours the formation of type structure only in the Sm-rich samples. It destroys this structure in the Nd-rich samples.

The process of forming 2223 phase from 2212 phase in Bi(Pb)-Sr-Ca-Cu-O System

The process of forming (2223) phase was studied by x-ray diffraction, thermal analysis, as well as electric and magnetic measurements. It was discovered that the formation of (2223) from (2212) is a phase transition-like process. Some possible mechanisms of (2212) to (2223) phase transition-like are discussed. Our results not only explain the difficulty for getting pure (2223) phase sample, but also give a way to prepare high quality (2223) phase sample.

Intrinsic pinning of domain walls in Dy(Fe1−xMx)2 (M = Ga, Al; x⩽0.2)

Abstract The magnetization and magnetization reversal process in pseudobinary compounds Dy(Fe1-xMx)2 (M = Ga, Al; x⩽0.2) have been investigated. A stepwise increase of magnetization with field can best be viewed on the virgin curves at low temperature while the staircase behavior of the demagnetization curve is observed only at 1.5 K. The temperature dependence of coercivity Hc(T) decays exponentially with increasing temperature from 4.2 K up to room temperature. Pronounced thermomagnetic history effects are also observed in the temperature dependence of the magnetization. It has been possible to account for the observed behavior in terms of the intrinsically pinned domain walls.

Structural and magnetic properties of Ce(Fe,M)12Nx interstitial compounds, M=Ti, V, Cr, and Mo

Stabilizing the 1‐12 phase with cerium was possible using a special heat treatment. The structural and magnetic properties of Ce(Fe,M)12 and their nitrides, for M=Ti, V, Cr, Mo, etc., were investigated using x‐ray‐diffraction and magnetic measurements. The effects of interstitial nitrogen atoms on lattice parameters, Curie temperature, saturation magnetization, and magnetocrystalline anisotropy are reported. A profound change was found on the magnetocrystalline anisotropy. As an example, in the case of CeMo2Fe10Nx, the easy magnetization direction changes from c axis to the basal plane depending on the nitrogen content x.

Neutron diffraction study of YFe10−xCoxMo2

YFe{sub 10{minus}{ital x}}Co{sub {ital x}}Mo{sub 2}(0 {le} {ital x} {le} 10) compounds were synthesized and studied by x-ray and neutron diffraction. Single phase samples with ThMn{sub 12}-type structure can be formed in the entire range of composition. Magnetic properties were studied at fields up to 70 kOe in the temperature range of 1.5 K to room temperature. X-ray diffraction analyses of aligned powders indicate that the easy magnetization direction is parallel to the {ital c} axis when {ital x}{le}6, and deviates from the {ital c} axis when {ital x}{ge}8. Neutron diffraction experiments show that the molybdenum atoms exhibit a strong preference for occupying the 8{ital i} sites, and cobalt atoms prefer to occupy the 8{ital f} and 8{ital j} sites.YFe10−xCoxMo2(0 ≤ x ≤ 10) compounds were synthesized and studied by x‐ray and neutron diffraction. Single phase samples with ThMn12‐type structure can be formed in the entire range of composition. Magnetic properties were studied at fields up to 70 kOe in the temperature range of 1.5 K to room temperature. X‐ray diffraction analyses of aligned powders indicate that the easy magnetization direction is parallel to the c axis when x≤6, and deviates from the c axis when x≥8. Neutron diffraction experiments show that the molybdenum atoms exhibit a strong preference for occupying the 8i sites, and cobalt atoms prefer to occupy the 8f and 8j sites.

Variation of magnetic properties as a function of Mo content in the RFe12−xMox series and their nitrides (R=Y, Nd, Gd)

The structure and magnetic properties of RFe12−xMox series and their nitrides with R=Y,Gd,Nd and x=0.8,1.0,1.5,2.0,2.5 have been studied by x‐ray‐diffraction and magnetic measurements. It is found that with the increment of Mo content x, the lattice parameters increase, whereas the saturation magnetization, Curie temperature, and anisotropy field decreases in the RFe12−xMox series. Upon nitrogenation lattice parameters, saturation magnetization, and Curie temperature increase. Correspondingly, the easy c‐axis magnetocrystalline anisotropy of the Fe sublattice decreases in YFe12−xMoxNy and GdFe12−xMoxNy but increases in NdFe12−xMoxNy although its variation with the Mo content is the same as in their original counterparts. NdFe12−xMoxNy compound in the low Mo content shows great potential for permanent magnet applications.

Magnetic properties of Si-substituted Y2Fe17

Abstract Magnetic properties of the Si-substituted Y 2 Fe 17 have been investigated. The Curie temperature increases with increasing Si content although the unit cell volume decreases. The average Fe magnetic moment decreases with Si substitution, and the easy magnetization direction does not change. Neutron-diffraction showed that the Si atoms do not preferentially occupy the dumbbell site. The occupancy of Si atoms is very small for the 6g site, and almost statistical for the other three sites.

Superconductivity and antiferromagnetic ordering in (Gd,Nd,Ce)2 CuO4

Abstract Magnetic and superconducting properties of Gd 1.85− x Nd x Ce 0.15 CuO 4 and Gd 2− x Ce x CuO 4 have been studied. The antiferromagnetic ordering temperature of Cu decreases with increasing Ce content in Gd 2− x Ce x CuO 4 and further decreases when Nd is substituted for Gd. In Gd 1.85− x Nd x Ce 0.15 CuO 4 , the antiferromagnetic ordering of Cu disappears at about x = 5 and superconductivity appears at about x = 0.8.The temperature - Nd concentration phase diagram for Gd 1.85− x Nd x Ce 0.15 CuO 4 is reported. Resistivity measurements reveal that the substitution of Nd for Gd results in an increase of charge carrier number. The antiferromagnetic ordering of Gd coexists with superconductivity at low temperatures. A possible explanation for the effect of Nd substitution is discussed.

Magnetic properties and crystal structure of melt-spun Sm(Co, M)7 (M = Al and Si) ribbons

Effect of Si and Al contents on the magnetic properties and crystal structure of melt-spun SmCo7-xMx (M = Al and Si) ribbons have been investigated. The Rietveld refinement results show that Al and Si prefer to occupy the 3g site in the TbCu7-type structure. The changes in both the magnetocrystalline anisotropy field and the microstructure with Si or Al substitution may account for the variation of magnetic properties. The coercivity of SmCo7−xSix ribbons is enhanced from 1.9 kOe for SmCo7 to 4.7 kOe for SmCo6.5Si0.5 and 2.6 kOe for SmCo6.95Al0.05, which is mainly because of the enhancement of magnetic anisotropy field by the Si and Al substitution for Co in 3g sites. Furthermore, in melt-spun SmCo7−xMx ribbons system, with increasing x, the grain size is slightly reduced for M = Si, but increased for M = Al. In addition, with further increasing x, the enhancement of coercivity is attributed to both the third element substitution for Co in 3g sites and grain refinement.Effect of Si and Al contents on the magnetic properties and crystal structure of melt-spun SmCo7-xMx (M = Al and Si) ribbons have been investigated. The Rietveld refinement results show that Al and Si prefer to occupy the 3g site in the TbCu7-type structure. The changes in both the magnetocrystalline anisotropy field and the microstructure with Si or Al substitution may account for the variation of magnetic properties. The coercivity of SmCo7−xSix ribbons is enhanced from 1.9 kOe for SmCo7 to 4.7 kOe for SmCo6.5Si0.5 and 2.6 kOe for SmCo6.95Al0.05, which is mainly because of the enhancement of magnetic anisotropy field by the Si and Al substitution for Co in 3g sites. Furthermore, in melt-spun SmCo7−xMx ribbons system, with increasing x, the grain size is slightly reduced for M = Si, but increased for M = Al. In addition, with further increasing x, the enhancement of coercivity is attributed to both the third element substitution for Co in 3g sites and grain refinement.

Intrinsic magnetic properties of R15B7Fe78 compounds

Tetragonal R15B7Fe78 (R=MM, Pr, Nd, Sm, Gd, and Y) compounds have been studied by x‐ray diffraction and magnetic measurements. The lattice parameters are found to decrease with increasing atomic number of rare‐earth elements, whereas the Curie temperatures TC increase monotonically, and the TC of Gd15B7Fe78 is the highest. The saturation magnetization and magnetocrystalline anisotropy were measured with a field up to 70 kOe at the temperature between 1.5 and 300 K. We found that the c axis is the easy axis of magnetization for R=Pr, Gd, and Y; the easy magnetization direction lies in the basal plane for R=Sm; and the direction of easy magnetization changes with temperature for R=Nd.