Zh. L. Jiang

Microstructure and magnetic properties of two-phase nanocomposite Nd9Fe85.5Nb1.0B4.5−yCy (y=0.5–4.5) magnets

Nanocrystalline two-phase Nd9Fe85.5Nb1.0B4.5-yCy magnets (y=0.5-4.5) have been prepared by melt spinning and subsequent heal treatment. The effect of remanence enhancement has been observed in the melt-spun ribbons after a proper annealing procedure. A two-phase nanocomposite Nd9Fe85.5Nb1.0B4.0C0.5 magnet with optimum magnetic properties of H-cj.=6.6 kOe, J(r)=10.22 kGs and (BH)(max)=13.32 MGOe has been obtained

The magnetic phase diagram of DyFe12-xMox (1.00 <= x <= 3.00)

The magnetocrystalline anisotropy and magnetic structure of DyFe12−xMox (1.00≤x≤3.00) have been investigated in detail by X-ray diffraction, thermomagnetic analysis, AC magnetic susceptibility, singular point detection technique and angular-magnetization measurement. A magnetic phase diagram of DyFe12−xMox (1.00≤x≤3.00) has been proposed. At room temperature, all DyFe12−xMox compounds exhibit uniaxial anisotropy. At low temperature, a spin reorientation transition of axis-to-cone was observed for DyFe12−xMox compounds with low Mo concentration, x<2.00. The spin reorientation temperature decreases with increasing Mo concentration. For DyFe12−xMox compounds with high Mo concentration, magnetohistory effects were observed below 48 K.

Crystallographic and magnetic properties of a Tb3(Fe,Cr)29 single crystal

A Tb-3(Fe,Cr)(29) single crystal with the monoclinic Nd-3(Fe,Ti)(29)-type structure was obtained after proper heat treatment on the original single crystal with a hexagonal structure grown by the Czochralski method. The magnetization curves along the hard and easy directions are presented. The lattice parameters are a = 1.058 nm, b = 0.848 nm, c = 0.968 nm, alpha = gamma = 90 degrees, and beta = 96.93 degrees, respectively. The Curie temperature is 477 K and the saturation magnetizations are 51.74 A m(2)/kg (18.07 mu(B)/f.u.) at 1.5 K and 58.34 A m(2)/kg (20.38 mu(B)/f.u.) at 293 K, respectively. Below room temperature, a first-order magnetization process of type II occurring at the critical field of 6.0 T at 100 K and 5.5 T at 200 K was observed. A magnetohistory effect taking place at about 175 K was also detected on the Tb-3(Fe,Cr)(29) single crystal

Magnetic properties of Tb2(Fe, Cr)17 single crystal

Synthesis of SIGN thin films on mirror-polished Si(100) substrates has been achieved by performing a bias-assisted hot filament chemical vapor deposition. High purity nitrogen, methane, and hydrogen were used as reactant gases. Incorporated Si element in the films totally came from the Si surface of the substrate. Scanning electron microscopy showed two categories of morphologies of the films according to the introduction of hydrogen. Energy-dispersive X-ray analysis and Auger electron spectroscopy depth profiling were used to measure the chemical composition of the samples. With no hydrogen applied, the film was found to be a nitride layer over the Si substrate with some nanosize columnal silicon-containing C-N crystals embedded. With hydrogen added, the film was uniformly composed of smaller SiCN particles. On both conditions, the overall carbon content was rather limited. X-ray photoelectron spectroscopy revealed the chemical environment of C, N, and Si atoms in the samples. The effect of methane flow ratio and substrate temperature were investigated on the conditions without hydrogen flow. The effects of hydrogen flow ratio on the films were also studied

Magnetic properties of Y2Fe15Cr2 single crystal

A Y2Fe15Cr2 Single crystal with the Th2Ni17-type structure has been prepared by the Czochralski method and investigated by means of Laue back-reflection, metallographic observation, X-ray diffraction, the singular point detection technique and magnetic measurements. A magnetohistory effect has been observed at a low temperature. Magnetization curves have been measured along the easy and hard directions in fields up to 6.5 T, The saturation magnetization and magnetocrystalline anisotropy field decrease with increasing temperature. The experimental magnetocrystalline anisotropy constant is in good a,areement with the calculation results on first approximation

A study of the magnetocrystalline anisotropy of Sm1−xDyxFe10.5Mo1.5(x = 0–1.0)

The magnetocrystalline anisotropy and the spin reorientation of Sm1−xDyxFe10.5Mo1.5 were investigated in detail. At room temperature, all Sm1−xDyxFe10.5Mo1.5 alloys possess easy c-axis anisotropy and the magnetocrystalline anisotropy field decreases with increasing Dy concentration. However, at low temperature, a spin reorientation transition of axis-to-cone type was observed in the Sm1−xDyxFe10.5Mo1.5 alloys with x ≥ 0.8. The spin reorientation temperatures increase with increasing Dy concentration in the Sm1−xDyxFe10.5Mo1.5 alloys.

Study on the Nanostructure and Magnetic Properties of NdFeNbB Permanent Magnets

Nd2Fe14B/-Fe nanocomposite permanent magnet contains the hard and soft magnetic phases, Nd2Fe14B and -Fe respectively. An exchange coupling effect exists between the two magnetic phases. The effect of alloying element Nb on its nanostructure and properties have been studied. Adding Nb to the alloy is effective to refine grains, a relatively small grain size causes a high intrinsic coercivity, remanence and therefore a high maximum energy product, (BH)max. MFM (Magnetic Force Microscope) was used to observe the magnetic micro-domain structure in the nanophase alloys. The length of the magnetic contrast shows a significant dependence on the microstructure and phase constitution, and the longer length is correspond with the larger exchange coupling effect between the soft and hard magnetic phases.

Study on the Magnetic Properties and Domain Structure of NdFeNbZrB Nanocomposite Permanent Magnets

A new kind of nanocomposite rare-earth magnets of Nd2Fe14B/ α-Fe were prepared by melt-spinning method. Effects of alloying element and processing parameter on the microstructure and magnetic properties of nanocomposite materials have been investigated. Zr is effective to enhance coercivity of alloys because of a refinement of grains, so that in alloy of Zr content with 1.0 at% (Zr1.0) has the smallest grain size of 17 nm and therefore causes the highest intrinsic coercivity . Addition of Zr can also enhance the ability of amorphous-forming. The combination of adding of Zr and using a smaller diameter of the nozzle in the melt-spinning method is effective for the forming of amorphous structure. According to the MFM study, the length of the magnetic contrast in the alloy is much larger than the mean grain size. The large length corresponds to that of interaction domains(ID), which is related to the exchange coupling effect.

Nanoscale structure and magnetic properties of Nd-Fe-Nb-B-C permanent magnets

We investigated the nanoscale structure and magnetic properties of Nd/sub 2/(FeNb)/sub 14/(BC)//spl alpha/-Fe. We studied several alloy compositions and the effect of C and Nb on the properties, and thus produced a new alloy of Nd/sub 9/Fe/sub 85.5/Nb/sub 1.0/B/sub 4/C/sub 0.5/. Its mean grain size is about 40 nm. Grain refinement enhanced the remanence, because of greater ferromagnetic exchange coupling between the hard and soft magnetic phase grains. Annealing improved the properties further. By optimizing the processing conditions, we obtained relatively high performance [J/sub r/=1.099 T, H/sub ci/=518.3 kA/m, J/sub r//J/sub s/=0.82, (BH)/sub max/=137.8 kJ/m/sup 3/] when the alloy was annealed at 700/spl deg/C for 15 min. We examined the magnetic domain structure in the nanophase alloy by magnetic force microscopy. The length of the magnetic contrast in the alloy is in the range of 450-550 nm, much bigger than the mean grain size. Here, we interpret the length in terms of interaction domains, which originate from the exchange coupling effect.

COMPARISON OF THE CRYSTALLOGRAPHIC AND MAGNETIC PROPERTIES BETWEEN TB2FE16.46CR1.23 AND TB3(FE, CR)29 SINGLE CRYSTALS

A novel Tb-3(Fe,Cr)(29) single crystal, which has a monoclinic Nd-3(Fe,Ti)(29)-type structure, is obtained using the Czochralski method by performing a proper heat treatment on the Tb2Fe16.46Cr1.23 crystal with a Th2Ni17-type structure. Thermomagnetic curves along the easy axis and magnetization curves along the easy and hard axes are presented for both crystals. The lattice parameters are a = 1.058 nm, b = 0.848 nm, c = 0.968 nm, alpha = gamma = 90 degrees, and beta = 96.93 degrees for the Tb-3(Fe,Cr)(29) single crystal. The Curie temperatures, saturation magnetizations, and magnetocrystalline anisotropy constants are compared between the Tb-2:17 and Tb-3:29 crystals. The magnetization behavior along the hard axis is quite different as a first-order magnetization process (FOMP) of type I for the Tb-2:17, but a FOMP of type LT for the Tb-3:29 crystal is observed below room temperature. At low temperatures, magnetohistory effects are detected for both crystals.