A detailed investigation of the structure and magnetic properties of R2Fe17-xGax (R = Tm, Er and Sm and x = 0-7) was carried out by means of powder X-ray diffraction, magnetization and AC magnetic susceptibility measurements. With increasing Ga content, a structural transformation from hexagonal Th2Ni17-type structure to rhombohedral Th2Zn17-type structure is observed in compounds Er2Fe17-xGax (x = 0-7) and Tm2Fe17-xGax (x = 0-7). The compounds Sm2Fe17-xGax (x = 0-7) crystallize in rhombohedral Th2Zn17-type structure. The Curie temperature increases in the initial Ga concentration range, reaches a maximum and then decreases at higher Ga concentration. The exchange interaction parameter JFeFe reaches a maximum and then decreases whereas the value of JRFe is almost independent of Ga concentration. X-ray diffraction measurements on magnetically aligned powder samples show a uniaxial anisotropy for compounds with at x = 2, 3 and 4 in the Sm2Fe17-xGax series whereas, it was observed for x = 7 in the Tm2Fe17-xGax compounds.

Upadhyayula V Varadaraju

Department Of Chemistry

K. V.S. Rama Rao

Crystallization

Erbium compounds

magnetic anisotropy

Magnetic susceptibility

Magnetic variables measurement

Magnetization

Permanent magnets

Samarium compounds

Thermoanalysis

Thulium

X ray powder diffraction

Curie temperature

Exchange interactions

INTERMETALLICS

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Structural, magnetic and exchange interaction studies on R2Fe17−xGax (R=Tm, Er and Sm) compounds

Physica B: Condensed Matter

Magnetic properties of (Sm0.5 Tb0.5) 2 Fe17-x Gax [mentioned subsequently as SmTbFe17-x Gax] have been investigated. All the compounds have formed in rhombohedral Th2 Zn17 structure with traces of α-Fe. The saturation magnetization decreases with increasing x and is attributed to the modification of the density of states of 3d band due to the low lying 3p band of Ga. The increase of Curie temperature up to x=3 and subsequent decrease is explained on the basis of band narrowing. The easy direction of magnetization is in the ab plane up to x=5 and changes along the c axis for x=7. © 2005 American Institute of Physics.

Fulltext

Journal of Applied Physics

Magnetic properties of SmTbFe 17-xGa x [0≤x≤8]

R2Fe17 (R = rare earth) intermetallic compounds constitute one of the most important classes of materials identified as high-energy permanent magnet materials. They crystallize either in the rhombohedral Th2Zn17 structure (for light R) or in the hexagonal Th2Ni17 structure (for heavy R). In this article, we discuss the variations in the lattice parameters (unit cell volume), site occupancies and Curie temperature when non-transition and transition metals are substituted for Fe in R2Fe17 compounds.

Physica Status Solidi (A) Applied Research

On the structural and magnetic properties of R2Fe17-x(A,T)x (R = rare earth; A = Al, Si, Ga; T = transition metal) compounds

Powder x-ray diffraction and magnetization measurements were employed to investigate the effect of Al on the structural and magnetic properties of Er2Co17-xAlx compounds with 0≤x≤4. Al substitution leads to a monotonic increase in the lattice parameters and an approximately linear decrease in the saturation magnetization. The Curie temperature is also found to decrease with Al concentration. Large thermomagnetic irreversibility seen in these compounds has been attributed to the domain wall pinning effect. The temperature variation of magnetization shows compensation points in the compounds with x = 3 and 4. The field-cooled magnetizations of these two compounds in low fields are found to be negative at temperature below the compensation temperatures, which has been explained on the basis of the temperature variations of the exchange coupling strengths of Er and Co sublattices. The easy magnetization direction at room temperature is found to be along the c-axis in all the compounds. The first order anisotropy constant at room temperature is found to increase with Al concentration, which has been attributed to the increase in the axial anisotropy of both the Er and Co sublattices as a result of Al substitution. © 2006 IOP Publishing Ltd.

Journal of Physics Condensed Matter

Effect of Al on the structural and magnetic properties of Er 2Co17-xAlx compounds

Powder neutron diffraction studies were carried out on (Ho1-xErx)2Fe15Ga2C y (x=0, 0.5, 1; y =0, 2) with a view to study the effect of substitution of Ga for Fe and the insertion of carbon at the interstitial sites on the structural and magnetic properties. All Ga substituted compounds (y=0) possess hexagonal Th2Ni17 type structure (space group: P63/mmc). However, the carbides adopt rhombohedral Th2Zn17 type structure (Space group: R3m). The unit cell volume increases with Ga substitution as well as with interstitial modification by carbon. An increase in the Curie temperature of about 260 K is observed for the compound HoErFe15Ga2C2 vis-a-vis HoErFe17. The increase is attributed to the preferential occupancy of Ga atoms in 18/(12j) and 18h(12k) sites and the presence of interstitial carbon. The magnetization increases with carbon addition. X-ray diffraction studies on magnetically aligned samples and neutron diffraction studies show that the easy magnetization direction lies in the basal plane at room temperature. © 1999 American Institute of Physics.

Neutron diffraction studies on (Ho1-xErx)2Fe15Ga2C y compounds

The structural and magnetic properties of HoErFe17-xGax (x = 0-7) were studied by means of X-ray diffraction and magnetization measurements. Powder X-ray diffraction studies show that the compounds transform from the hexagonal Th2Ni17 structure (x ≤ 4) to rhombohedral Th2Zn17 structure (x ≥ 5) with increasing Ga concentration. The substitution of Ga for Fe leads to an increase in lattice constants a, c and unit-cell volume v. The Curie temperature is found to first increase and then decrease with increasing Ga concentration, attaining a maximum value of 535 K at about x = 4, which is 207 K higher than that of HoErFe17. Both iron sublattice anisotropy and rare-earth sublattice anisotropy are found to be modified by the introduction of the Ga atoms and have been confirmed through X-ray diffractograms of magnetically aligned samples. © 1998 Elsevier Science B.V. All rights reserved.

Journal of Magnetism and Magnetic Materials

Structural and magnetic properties of HoErFe17-xGax compounds

An x-ray diffraction study of (Pr0.5Er0.5)2Fe17-xAlx (0≤x≤10) shows an expansion of its unit cell with x. The crystal structure changes from hexagonal Th2Ni17 to rhombohedral Th2Zn17 at x = 6. The magnetic moment decreases by increasing the Al concentration. This effect may be due to the charge transfer from Al to the 3d band of Fe. The Curie temperatures are found to increase with Al up to x = 3 and then decrease up to x = 10, and the possible underpinning mechanisms are discussed. X-ray diffractograms of the magnetically aligned samples indicate that the easy magnetization directions of the samples with x = 1,2,3, and 4 lie on a cone about the c axis. Electrical resistivity measurements show that the residual resistivity increases drastically with the Al concentration. The temperature coefficient of resistivity becomes almost zero for intermediate Al concentrations. © 1995 American Institute of Physics.

Structural, magnetic, and electrical properties of (Pr0.5Er0.5)2Fe17-xAlx

Journal of Physics: Condensed Matter

Magnetocrystalline anisotropy of non-uniaxialR-Tmagnetic materials studied by the singular point detection technique: an application to compounds (R = Y or Gd andx= 0 or 1)

Structural and magnetic studies of Er2Fe17−xMxCy (M=Ga and Al) compounds

Structural, magnetic and exchange interaction studies on R2Fe17-xGax (R = Tm, Er and Sm) compounds

Journal	Data powered by TypesetPhysica B: Condensed Matter
Publisher	Data powered by TypesetElsevier Science Publishers B.V., Amsterdam
ISSN	09214526
Open Access	No