Senlin Ge

Magnetic and crystallographic properties of novel Fe‐rich rare‐earth nitrides of the type RTiFe11N1−δ (invited)

We succeed in inserting a number of nitrogen atoms into the RTiFe11 intermetallics. The nitrides retain the ThMn12‐type structure, but with an increase in the unit cell volume. The crystallographic sites located by nitrogen atoms are determined by using neutron diffraction techniques. The nitrogen atoms are found to have an effect of increasing Curie temperature and saturation magnetization. Moreover, an essential change in magnetocrystalline anisotropy is observed upon nitrogenation. By all of these effects, the NdTiFe11N1−δ compounds have excellent intrinsic magnetic properties favorable for permanent magnet applications.

New potential hard magnetic material-NdTiFe11Nx

Abstract The absorption of nitrogen in ternary compounds of the type RTiFe 11 has been studied, where R = Y , Nd , Sm . X-ray diffraction showed that the tetragonal structure ( I 4/ mmm ) is retained but that the unit cell volume is slightly increased. Furthermore, nitrogen absorption both increases the Curie temperature, and gives rise to a drastic changing of magnetocrystalline anisotropy in RTiFe 11 N x compounds. Among them, NdTiFe 11 N x now has high magnetization, high Curie temperature and easy axis magnetocrystalline anisotropy potentially suitable for permanent magnet applications.

NEUTRON DIFFRACTION STUDY OF THE NITRIDE YTIFE11NX

Abstract A neutron diffraction study was carried out on a powder sample of the composition YTiFe 11 N 0.5 at 300 K. Neutron diffraction measurements not only confirm that the nitride maintains the tetragonal structure of its virginal compound YTiFe 11 ( ThMn 12 - type , I 4/ mmm ), but also indicate that the nitrogen atoms occupy the interstitial 2b sites. A detailed analysis of the crystallographic and magnetic structure is presented, and the relationship of the magnetic properties to the crystallographic structure is discussed in this paper.

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.

Neutron diffraction study of Y2Fe14BN1−δ

Abstract The studies of the crystallographic and magnetic properties of R2Fe14BN1−δ, where R represents Nd and Y, have been carried out by neutron diffraction techniques and magnetic measurements. Upon nitrogenation, the tetragonal structure of R2Fe14B is retained, but the unit cell volume is slightly increased. The refinement of neutron data indicates the nitrogen atoms occupy the 4f interstices in the nitrite of Y2Fe14B. In the consequence of filling these interstices, the Curie temperatures of these nitrides are increased about 60 K, wheres, their saturation moments and anisotropy fields are a little inferior to their virginal counterparts. In order to explain the changes of the magnetic properties, we give a brief discussion about the relationship between the magnetic properties and the crystallographic structure of these nitrides.

MAGNETIC PROPERTIES OF ANISOTROPIC ND(FE,MO)12NX POWDERS

Anisotropic magnets based on Nd(Fe,Mo)12Nx nitrides were prepared by a milling process. Particle size dependence of the coercivity has been investigated. The optimizing size which accompanies the highest coercive force was examined by transmission electron microscopy. A coercive force iHc of up to 6.2 kOe, and a maximum energy product (BH)max of up to 12.0 MG Oe were obtained. The mechanism of the coercivities is discussed with a comparison of the powders prepared by mechanical alloying. The variation of coercive force as a function of temperature is reported.

EFFECT OF INTERSTITIAL NITROGEN ON THE STRUCTURAL AND MAGNETIC PROPERTIES OF NDFE10.5V1.5NX

The NdFe10.5V1.5Nx nitrides crystallize in the ThMn12-type structure. The nitrogen atoms occupy interstitial sites, and their most important effects are on the crystal fields around the rare earth ion sites. The variation of anisotropy fields of NdFe10.5V1.5Nx as a function of the nitrogen content x is presented. The crystal field interaction parameters are determined by using single-ion model. In the light of this study, high performance magnetic powders based on NdFe10.5V1.5Nx were successfully prepared.

57Fe Mössbauer study of RTiFe11Nx compounds

Abstract The 57Fe Mossbauer spectra of some nitrides of the type RTiFe11Nx (R = Gd, Tb, Dy, Ho and Y) have been measured at room temperature. The magnetic behaviour of Fe atoms at different sites in RTiFe11Nx have been investigated. The interstitial nitrogen atoms lead to an increase both in effective hyperfine fields and in isomer shifts. It is also shown that there are slight differences in effective hyperfine fields for the various RTiFe11Nx compounds.