1. Didier Hérisson, Michael Östh and Per Nordblad Uppsala University
Experimental first order reversal curves (FORC) on Ising and Heisenberg spin glasses
Didier Hérisson, Michael Östh and Per Nordblad
Uppsala University

2. Hysteresis loops on spin glasses
Au(Fe) – E.I. Kondorski
et al. (1973)
Cu(Mn)-P. Monod et al.
(1979)
(From Spin Glasses, R. Rammal and J. Souletie, notes from
a course at Grenoble in 1981)

3. What can one learn from the hysteresis behaviour using FORCs?
The FORC distribution gives a visualisation of switching events
Comparison with ’related’ systems
Distinguishes an in-field SG phase from no in-field SG phase?

4. The FORC method
Roberts et al. J. Geophys.
Res. 105, (2000)

5. Construction of the FORC distribution

6. FORC distributions C.R. Pike et al. Geophys. J. Int. 145, 721 (2001)
b) Weakly interacting
nanoparticles
c) Floppy disc.
d) nanoparticles

7. Monte Carlo 2d-EASG
H. G. Katzgraber et al. Phys. Rev. Lett. 85, (2002)

8. 3D FORC distribution plot from MC-simulations of a 2d Ising EASG
H.G. Katzgraber et al.

9. ZFC-FC-TRM
H=0.1 Oe
Ag(Mn)
FMTO

10. Hysteresis of Ag(Mn) and Fe0.5Mn0.5TiO3

11. FORC FMTO
M (arb.units.)

12. FORC distribution FMTO

13. FORCs Ag(Mn)

14. FORC distribution Ag(Mn)

15. 3D FORC Ag(Mn)

16. Comparison
FMTO
Ag(Mn)

17. Conclusions
Remarkably different hysteresis behaviour for Ising (strongly anisotropic) and Heisenberg spin glasses.
The FORCs of FMTO shows similarities with weakly interacting nanoparticle systems with wide distributions of particle sizes.
The Ag(Mn) system yields unique FORC distributions with a very sharp structure at a rather weak negative bias field and low coercivity……
Supportive of other experimental indications suggesting in-field SG transitions in weakly anisotropic systems?

18. FeAgW – mechanically alloyed

19. FeAgW - FORC
FeAgW
c.f. FMTO