Yun-Xi Sun

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.

Ferromagnetic properties and structures of the Mn-implanted GaAs semiconductor

Submicron ferromagnets have been successfully incorporated into semi-insulating (001) GaAs crystals by Mn+ ion implantation and subsequent rapid annealing. Magnetization measurements reveal room-temperature ferromagnetism. The structural and compositional properties of crystallites have been analyzed by transmission electron microscopy, energy dispersion x-ray spectrum, and electron microdiffraction. The results show that crystallites of MnGa and MnAs with a small amount of Ga are formed. Atomic force microscopy and magnetic force microscopy images indicate that the single-domain magnetic state is dominant in submicron ferromagnets under our annealing conditions (750u200a°C–900u200a°C).

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.

The magnetization properties of high-Tc superconductor YBa2Cu3O∼7 at low magnetic fields

Abstract The magnetization of a high-Tc superconductor YBa2Cu3O∼7 was measured at low magnetic fields (

Neutron diffraction study of Nd5Fe17

Abstract Nd 5 Fe 17 is a new stable phase in the binary Nd–Fe system. X-ray diffraction of single crystals revealed a complex structure belonging to the hexagonal space group P6 3 /mcm. We perform a neutron diffraction study of Nd 5 Fe 17 powders. Position parameters, occupation of atoms, magnetic moment, coordination number, and average bond length in the hexagonal structure are reported.

Determination of flux pinning potentials from field-induced anisotropy in oxide superconductors

Abstract The angular dependence of magnetization of YBa2Cu3O7 and YBa2Cu2.85 Ag0.15O7 was measured at 77K by rotating the sample with respect to the cooling field. The distribution of the depth of pinning potential wells for flux lines can be determined. It is unsymmetrical and can be well described by the Rayleigh distribution. The average depth for a single pinning potential well is about 0.2 eV for YBa2Cu3O7 at 77K.

Study of permanent magnetic properties of the 1‐12 nitrides with Nd and Pr

The permanent magnetic properties of isotropic and anisotropic powders of R(Fe,Mo)12Nx compounds, where R=Pr and Nd, were investigated by using mechanical alloying and a conventional milling process. For the isotropic magnetic powders, a coercive force of up to 9 kOe and a maximum energy product of 6.6 MGOe were obtained in Nd compounds, while with the anisotropic powders a maximum energy product of 12 MGOe was achieved. In the isotropic Pr(Fe,Mo)12Nx compounds the best result were 4.5 MGOe for (BH)max and 6.0 kOe for iHc. The temperature dependence of coercive force has been investigated in a temperature range between 300 and 500 K, and the results are reported in a comparison with that of Nd‐Fe‐B magnets.

Magnetic properties of RFe10Si2Cx prepared by arc-melting (R=Y, Gd, Dy, and Er)

Abstract Samples of RFe10Si2Cx with R = Y, Gd, Dy, and Er; x = 0, 0.1, 0.3, and 0.5 were prepared by arc-melting. X-ray diffraction and thermomagnetic analyses showed that intersitial carbides with the ThMn12 structure are formed. Similar to R2Fe17Cx, the amount of C in the interstitial carbides is much smaller by arc melting than that by gas-solid reaction. Lattice expansion and Curie temperature enhancement are observed, but the effects of C addition are small. Spin reorientation temperatures of DyFe10Si2 and ErFe10Si2 decrease due to the interstitial C atoms.