1 / 25

Three-dimensional magnetization process in HoFe 11 Ti

Three-dimensional magnetization process in HoFe 11 Ti. Yuri Janssen, J.C.P. Klaasse, E. Br ü ck, F.R. de Boer, K.H.J. Buschow, J. Kamar á d 1 , N.V. Kudrevatykh 2. I. M. II. B. 1: Institute of Physics, Praha 2: Institute of Physics and Applied Mathematics, Ekaterinburg. Outline

blaine
Download Presentation

Three-dimensional magnetization process in HoFe 11 Ti

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Three-dimensional magnetization process in HoFe11Ti Yuri Janssen, J.C.P. Klaasse, E. Brück, F.R. de Boer, K.H.J. Buschow, J. Kamarád1, N.V. Kudrevatykh2 I M II B 1: Institute of Physics, Praha 2: Institute of Physics and Applied Mathematics, Ekaterinburg

  2. Outline • Introduction • Experiment • Results • Conclusion

  3. Research of rare-earth (R) – transition-metal(T) compounds Modern permanent magnets: - SmCo5 (1960s) - Nd2Fe14B (1984) - RFe11Ti (1990s) Requirements: - large magnetization - high ordering temperature - high coercivity  large magnetocrystalline anistropy

  4. Magnetic R-T coupling essential for coupling between: - large magnetization (T) - high anisotropy (R) Hund’s rules ==> Light-R (Nd, Sm) – T : parallel coupling => ferromagnets Heavy-R (Gd, ..Ho, Tm) – T : antiparallel coupling => ferrimagnets MR MT M MR MT M

  5. HoFe11Ti Tetragonal crystal structure: ThMn12-type(s.g. I4/mmm) Ti stabilizes crystal structure [001] [100] [010]

  6. HoFe11Ti: R-T coupling strong!  Ho and Fe sublattice moments remain antiparallel B MFe = 20 mB/f.u. M = 10 mB/f.u. [001] [001] MHo = 10 mB/f.u.

  7. Strong coupling  HoFe11Ti excellent system for research on magnetocrystalline anisotropy HoFe11Ti: easy-axis system ( M // [001] ) Tetragonal structure  Eanisotropy = K1sin2q + K2 sin4q + K3 sin6q + K4 sin4qcos4f + K5sin6qcos4f [001] q Ho has large orbital momentum ==> at low temperature, higher order K play a role [010] f [100]

  8. Magnetic free energy determines equilibrium magnetization F = Eanisotropy + EZeeman = Eanisotropy- B.M Only K1 Higher order K

  9. Outline • Introduction • Experiment • Results • Conclusion

  10. MS Bdem ~ 0.3 T Magnetization B // main directions Magnetic-phase transition when field in plane Different in-plane results!  K4, K5 important

  11. HoFe11Ti : possible 3D-process  3D magnetometry (SQUID, high-field magnet) Requirements: - Pickup coils in three directions - Sample single domain (homogeneous magnetization)

  12. Sample single domain: projection of B on [001] Choose y[001] = 75°  single domain when B ~ 1.1 T

  13. Magnetization for B in (110) plane MS sin 75 Above 1.1 T, sample single domain Transition occurs above 1.1 T

  14. Magnetization for B in (100) plane MS sin 73 Above 1.1 T, sample single domain Transition occurs above 1.1 T

  15. Measurement configuration Mz // B Mx near [001] My Mx Mz After measurement: project Mx, My, Mz on [100], [010], [001]

  16. Outline • Introduction • Experiment • Results • Conclusion

  17. Magnetization for B in (110) plane My nearly zero Conclusion: 2D process

  18. Magnetization for B in (110) plane Projection on crystal axes Magnetization for [100] and [010] equal, as expected

  19. Magnetization for B in (100) plane My becomes non-zero!  3D process

  20. Magnetization for B in (100) plane Projection on crystal axes B in (100) plane: 3D process

  21. Transition: first-order (follows from coexistence) Outlook: mechanism for coexistence ?  microscopy

  22. Calculations based on anisotropy parameters* B = 3 T B in (110) plane 2D process First order B = 4 T Abadìa et al., J. Phys.:Condens. Matter 10 (1998), 349 Calculations: M.-H. Yu

  23. B = 5 T B in (100) plane 3D process First order B = 6 T

  24. Conclusions: • At the magnetic phase transition, • a 3D magnetization process occurs • - This phase transition is first order

  25. Some combinations of K1, K2, K3 (..K4, K5) ==> local minima in magnetic energy as a function of angle with [001] ==> First order magnetization process (FOMP)* M  [001] M // [001] * Asti and Bolzoni, J. Magn. Magn. Mater. 20 (1980), 29

More Related