Gui-Chuan Liu

MAGNETIC-PROPERTIES OF A NOVEL SM3(FE, TI)29NY NITRIDE

A new interstitial nitride of Sm3(Fe0.933Ti0.067)29Ny (y=5) has been synthesized. Its x‐ray pattern can be indexed in Nd3(Fe,Ti)29‐type monoclinic symmetry with the lattice parameters of a=1.098 nm, b=0.882 nm, c=0.985 nm, and β=97.50°. The Sm3(Fe0.933Ti0.067)29Ny nitride exhibits ferromagnetic ordering with a Curie temperature Tc=750 K. The saturation magnetization Ms is 160 A m2/kg at 4.2 K and 140 A m2/kg at 293 K. The anisotropy field is 18.1 T at 4.2 K and 12.8 T at 293 K. The coercivity of μ0iHc=0.83 T at 293 K on this new nitride has been developed.

Magnetic properties of R3(Fe,Ti)29Cy carbides (R=Nd, Sm)

R3(Fe, Ti)29Cy carbides (R=Nd, Sm) have been synthesized by gas-solid phase reaction. The Curie temperature is enhanced by carbonation, with values of 651 K and 641 K for Nd and Sm carbides respectively. The saturation magnetization of the carbides is slightly lower than that of their parent alloys. The Sm carbide has a large uniaxial anisotropy field, 21 T at 4.2 K and 14 T at 293 K. A coercivity of mu 0iHc=0.3 T at room temperature in the Sm carbide has been developed.

Magnetic properties of R2Fe17Cx compounds (R = Y, Sm and Er, x∼2)

Abstract The interstitial carbides R2Fe17Cx (x∼2) have been prepared by gas-phase modification with acetylene for R = Y, Sm and Er. The average iron magnetic moments derived from the magnetizations of Y2Fe17Cx at temperatures of 1.5 K and 293 K respectively are 34.1 μB/f.u. and 28.9 μB/f.u.. The anisotropy fields of Sm2Fe17Cx at T = 1.5 K and 293 K are respectively 21.7 T and 13.5 T. A spin reorientation transition was observed at 124 K for Er2Fe17Cx.

Study of the magnetocrystalline anisotropy of YFe12-xMox and YFe12-xMoxNy (x=1-3, y approximately=1)

The magnetocrystalline anisotropy of YFe12-xMox and YPe12-xMoxNy (x=1-3, y approximately=1) have been investigated by X-ray diffraction and the singular point detection technique. The uniaxial anisotropy of the YFe12-xMox series decreases with increasing Mox concentration with a clear turning point at about x=1.6. The anisotropy characteristic of the nitride YFe12-xMoxNy changes into a canted-type anisotropy for x or=1.5. The anisotropy reduction for YFe12-xMox is mainly due to the substitution of Mox atoms on the 8i sites, while the further change in anisotropy for YFe12-xMoxNy may be due to a change in the 3d orbital moment or to a change in crystal-field interaction by the interstitial Ny atoms.

Magnetic properties of NdFe12 − xVx and NdFe12 − xVxNy (x = 1–3)

Abstract The iron-rich intermetallic compound NdFe 12 − x V x ( x = 1–3) and its nitrides NdFe 12 − x V x N y have been investigated. For NdFe 12 − x V x , the Curie temperature T C , the saturation magnetization M s and the anisotropy field B A decrease with increasing V concentration. NdFe 12 − x V x N y has a T C of about 750 K, B A of about 8 T and M s in the range 150 – 122 J T −1 kg −1 with x = 1.25 – 2.5.

STUDY OF MAGNETOHISTORY EFFECTS IN YFE12-XMOX (X=1.5-3.0)

Magnetohistory effects in YFe12−xMox (x=1.5–3.0) have been investigated. The freezing temperature Tf increases with increasing Mo concentration. Irreversible behavior still appears in an applied field up to 6 T for YFe9.5Mo2.5. These magnetohistory behaviors may be understood by domain‐wall pinning.

Hard magnetic properties of the novel compound

The novel nitride with monoclinic structure is synthesized by gas - solid reaction. Its hard magnetic properties have been investigated by ball milling and magnetic measurements. The intrinsic coercivity increases with decreasing average particle size d and, after reaching a maximum at , then decreases slowly. increases also with increasing magnetizing field. A value of has been attained. The magnetizing field for obtaining coercivity saturation is about 1.5 T. The hard magnetic properties of remanence and energy product for are achieved at 293 K.

Sm2Fe17Ny powder with high coercivity prepared by high energy ball milling

Abstract Isotropic Sm 2 Fe 17 N y powder was prepared by ball-milling from the parent alloy of Sm 2 Fe 17 , subsequent nitriding. The room-temperature coercivity up to 31.3 kOe was acheived. The maximum energy product was derived to be 10.5 MGOe with a remanence of 7.0 kGs. The anisotropy field H a of this nitride is 180 kOe determined by SPD technique.

Magnetic properties of PrFe12 − xMox and PrFe12 − xMoxNy (x = 1–2.5)

Abstract A series of PrFe 12 − x Mo x compounds with x = 1.0, 1.25, 1.5, 1.75, 2.0, 2.25 and 2.5 and their nitrides with ThMn 12 -type structure were prepared and investigated. The PrFe 12 − x Mo x compounds are characteristic for planar anisotropy. However, the nitrides are uniaxial in the magnetic ordering temperature. The intrinsic magnetic properties, T c , M s and B a enhance with decreasing Mo concentration.

Magnetic properties of novel compounds R3(Fe,Cr)29Xy (R=Nd, Sm and X=N, C)

Abstract The novel ternary rare-earth iron-rich interstitial compounds R 3 (Fe,Cr) 29 X y (R=Nd, Sm and X=N, C) with the monoclinic Nd 3 (Fe,Ti) 29 structure have been successfully synthesized. Introduction of the interstitial nitrogen and carbon atoms led to a relative volume expansion ΔV / V of about 6% and an enhancement of Curie temperatures T c about 268 K for the nitride and about 139 K for the carbide, respectively. The Nd 3 Fe 24.5 Cr 4.5 X y compounds have a planar anisotropy at room temperature. A first-order magnetization process (FOMP) with critical field B cr =4.4 T and 3.1 T at room temperature were observed for the Nd-nitride and carbide compounds, respectively. The Sm 3 Fe 24 Cr 5 X y compounds were found to have a large uniaxial anisotropy of about 18 T at 4.2 K and about 11 T at 293 K. A FOMP with B cr =2.3 T was also observed in the Sm-nitride compounds at 4.2 K. Magnets with coercivity of μ Oj H c ∼0.8 T at 293 K has been successfully developed from the Sm 3 Fe 24 Cr 5 X y (XN and C) phases.