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Abstract

The direction of spontaneous magnetisation at 0 K across a phase orientation boundary in rare-earth laves phase compounds is computed as a function of the ratio of magnetic to electrostatic interactions. The phase boundary and range of parameters used for the computation correspond to the portion of the orientational phase diagram where experimental data can be obtained. In the series of pseudo-binary compounds (Gdx Ho1-x )Co2 and (Yx Ho1-x )Co2 the range of parameters covers the continuous transition from the <100> to the <110> orientations. The nmr measurements on this series show that the direction of spontaneous magnetisation is at intermediate orientation between the <100> and <110> directions. The material TmFe2, which is in the vicinity of a discontinuous orientational boundary, is also discussed.

 

 

Keywords

Lanthanides Crystal field Laves phase Phase transition.

Article Details

References

  1. McCausland, M.A.H. and Makenzie, I.S. Nuclear Magnetic Resonance in Rare earth Metals, Taylor and Francis Ltd., London, 1980.
  2. Bunbury, D.St.P., Carboni, C., McCausland, M.A.H., Cone, R. and Mroczkowsky, S. and Ross, J.W. The hyperfine splitting of the ground state and first excited state of holmium in yttrium hydroxide. J. Phys. Condens. Matter. 1995,7, 6125-6136.
  3. Koehlera, M.R., Garleab, V.O., McGuirec, M.A., Jiaa, L., Keppensa, V. Spin reorientation and magnetoelastic coupling in Tb6Fe1−xCoxBi2 (x = 0, 0.125, 0.25, and 0.375) alloy system. J. Alloys and Compounds, 2014, 615, 514–520.
  4. Al Abry, E. 2003 M.Sc. Thesis, The orientation of the direction of spontaneous magnetization of rare-earth ions at a site of cubic symmetry. Department of Physics, College of Science, Sultan Qaboos University, Sultanate of Oman.
  5. Carboni, C., Al-Abry, E. and Arafin, S. The direction of spontaneous magnetisation of lanthanide ions at a site of cubic symmetry. SQU J. Science, 2007, 12(1), 53.
  6. Stevens, K.W.H. Matrix elements and operator equivalents connected with the magnetic properties of rare earth ions, Proc. Physi. Soci., A, 1952, 65, 209.
  7. Lea, K.R., Leask, M.J.M. and Wolf, W.P. The raising of angular momentum degeneracy of f-electron terms by cubic crystal fields. J. Phys. Chem. Solids, 1962, 23, 1381-1405.
  8. McMorrow, D.F., McCausland, M.A.H., Han, Z.P. Exchange and crystal field interaction of Ho3+in a GdAl2 single crystal: an NMR study. J. Phys Condens. Matter, 1989, 1, 10439-10458.
  9. Gignoux, D., Givord, F., and Lemaire, R. Magnetic properties of single crystals of GdCo2, HoNi2 and HoCo2 Phys. Rev B, 1975, 12, 3878-3884.
  10. Aubert, G., Gignoux, D., Givord, F., Lemaire, R. and Michelutti, B. Magnetization reorientation in HoCo2, Solid State Commun, 1978, 25, 2, 85–87.
  11. A Castets, D Gignoux and B Hennion, New aspects of the magnetic excitations in HoCo2. Phys. Rev. B, 1982, 25, 337-348.
  12. Germano, D.J. and Butera, R.A. Heat capacity of, and crystal field effect in, the RFe2 intermetallic compounds, Phys. Rev. B, 1981, 24(7), 3912-3927.
  13. Martin, K.N., de Groot, P.A.J., Rainford, B.D., Wang, K., Bowden, G.J., Zimmermann, J.P. and Fanghor, H. Magnetic anisotropy in the cubic Laves REFe2 intermetallic compounds. J. Phys. Condens. Matter, 2006, 18, 459- 478.
  14. Atzmony, U., Dariel, M.P., Bauminger, E.R., Lebenbaum, D., Nowik, I. and Ofer, S. Spin-orientation diagrams and magnetic anisotropy of rare-earth-iron ternary cubic laves compounds. Phys. Rev., 1973, B 7, 4220-4232.
  15. Yanovsky, R., Bauminger, E.R., Levron, D., Nowik, I. and Ofer, S. Crystalline fields, exchange interactions and spin reorientations in TmxHo1−x Fe2 systems, studied by a 170Yb Mössbauer probe. Solid State Commun. 1975, 17, 1511-1514.
  16. Rhyne, J. and Koon, N.C. Magnetic excitations in HoFe2. J. Appl. Phys., 1978, 49, 2133-2135.
  17. Koon, N.C. and Rhyne, J. Excited state spin waves in ErFe2. Solid State Commun., 1978, 26, 537-540.
  18. Bleaney, B., Bowden, G.J., Cadogan, J.M., Day, R.K. and Dunlop, J.B. A Mossbauer study of the cubic Laves phase intermetallic compound TmFe2. J. Phys. F, Met. Phys., 1982, 12, 795-811.
  19. Waind, P.R., Mackenzie, I.S. and McCausland, M.A.H. Anisotropy and asymmetry of the hyperfine spectrum of holmium in magnetically ordered RAl2 alloys. J. Phys F, 1983, 13, 1041-1056.
  20. Carboni, C., Mackenzie, I.S. and McCausland, M.A.H. Nuclear Magnetic Resonnance at microwave frequencies, Hyperfine Interactions, 1989, 51, 1139-1144.
  21. Bunbury, D.StP., Carboni, C., McCausland, M.A.H. and Prakash, O. NMR studies of spin reorientation in (Ho,Gd)Co2. Unpublished Proc. XXIII Congress Ampere (Istituto Superiore di Sanita Roma), 1986.
  22. Al Sariri, M. M.Sc. Thesis, Crystal Field and Magenic Anisotropy in TmFe2. Department of Physics, College of Science, Sultan Qaboos University, Sultanate of Oman, 2010.
  23. Carboni, C. Anisotropy in RFe2 intermetallics: an nmr study. SQU J. Science, 2009, 14(1), 71-83.