SPSRM, Saclay, France in the eighties

Transcription

1 J.M. Hammann Miguel Ocio C. Pappas SPSRM, Saclay, France in the eighties M. Alba 1/20

2 Scaling in spin glasses M. ALBA, LLB [CEA-CNRS] Master curves in effective time of the TRM relaxations of CsNiFeF 6 in very low magnetic fields Time scaling in CsNiFeF 6, Ocio, Alba, Hammann J. de Phys. Lett. 46 (85) /20

3 Time scaling in spin glasses and aging in disordered systems Content of the talk Polymers, aging and time scaling Time scaling in CsNiFeF 6, the start of it CdCr 2 S 4, other spin glasses and other systems Polymers CdCr 2 S 4 CsNiFeF 6 3/20

4 Time scaling in disordered systems Content of the talk Polymers, aging and time scaling Time scaling in CsNiFeF 6, the start of it L. C. E. STRUIK, Physical ageing in amorphous polymers and other materials, Elsevier, 1978 CdCr 2 S 4, other spin glasses and other systems 4/20

5 Physical aging and time scaling in polymers tw Machine and procedure Stress and strain experiment Age: time spent below TG before the start of the strain, up to 4 years or more. Short term behaviour : shape invariance if t< tw Shift proportional to t/twµ 5/20

6 Non-sationarity, time scaling and effective time For the short term behavior t< t w, time scaling variable: t/t w µ Definition of a time scaling exponent µ varying with temperature (T β < T <T G ) and constraint. µ =1 full aging, µ =0 no aging Reversibility of the physical aging: a temperature excursion above T G rejuvenate the sample Aging during the measurement: age t a =t w +t leading to an effective time λ to integrate the aging effects during the measurement Temperature dependence of µ Constraint dependence of µ 6/20

7 Non-sationarity, time scaling and effective time Effective time λ to study the relaxation at constant age and predict the long term behavior of the mechanical properties for t>> t w Predictions always done in real creep times Effective time Consecutive aging tests 7/20

8 Master curve and streched exponantial Universal behavior of the aging properties of amorphous polymers in the deep aging regime (µ 1) Unified master curve for the momentary part of the relaxation after scaling of the compliance J o and of the relaxation times t o Stretched exponential curve with an exponent β 1/3 Universal master curve of polymer aging 8/20

9 Aging in spin glasses Content of the talk Polymers, aging and time scaling Time scaling in CsNiFeF 6, the start of it CdCr 2 S 4, other spin glasses and other systems Aging of TRM in CsNiFeF 6 tw1=140 s tw2=1000 s tw3=10000 s tw4=86000 s 9/20

10 Time scaling in spin glasses CsNiFeF 6 : insulating compound with a modified pyrochlore structure Spin glass below 5.2 K with a high mean value J 0 of the magnetic interaction TRM: Thermo Remanent Magnetisation σ(t,t w ) Relaxation of the TRM in very low field H=15 mg as a function of the waiting time t w Shifts: vertical unusual (the TRM decreases with t w ) and horizontal with an effective time and a time exponent µ tw1=140 s tw2=1000 s tw3=10000 s tw4=86000 s Pyrochlore Magnetic lattice 10/20

11 Time scaling in spin glasses First master curves in effective time: Scaling for t<t w and t>t w Parameter µ: smaller than 1, definitely TRM relaxation fitted by the product of a stationary and an aging part: a power law (small exponent α temperature depenedent) et a stretched exponential (exponent β and relaxation times varying with temperature) «Moustaches» due to intrinsic SQUID relaxations after the field change Master curves in effective time In CsNiFeF 6 and exponent µ Time scaling in CsNiFeF 6, Ocio, Alba, Hammann J. de Phys. Lett. 46 (85) /20

12 Aging in spin glasses Aging of the TRM in AgMn 2.6% Ocio, Alba, Hammann Euro. Phys. Lett. 2 (86) 45 Canonical spin glasses : intermetallic like AgMn, AuFe, insulating CdCr 2 S 4 Criterium of the spin glass definition: broad distribution of relaxation times and nonstationarity Signature of the glassiness 12/20

13 Other Spin Glasses and other types of experiments First experiments on the TRM by the UCLA group of R. Orbach Simple stretched exponential Metallic and insulating spin glasses R.V. Chamberlain et al, PRL 52 (1984) 867 First experiments on the Zero Field Cooled magnetisation (ZFC) and on the x by the Upssala group of L. Lundgren Scaling variable t/t w Metallic spin glass CuMn L. Lundgren et al, PRL 51 (1983) 911 Lundgren et al, PRL 51 (83) /20

14 M. Ocio and the technics Electronics: AC susceptometers Power supplies Adaptators of all sorts SLUGS and SQUIDS Home made SLUGS Superconducting coils: excitation and detection AC SQUIDS: 300 Mhz, 88 Mhz DC SQUIDS Cryogenics : Dilution fridges He 3,He 4 cryostats Talk of Patrick Pari, this afternoon Low field SQUID susceptometer Built in Saclay in the eigthies 14/20

15 Aging in spin glasses and time scaling in disordered systems T rejuvenation T memory effect Multiple memories in the x suceptibility of CdCr 2 S 4 V. Dupuis, Ph. D, 2002 Content of the talk Polymers, aging and time scaling Time scaling in CsNiFeF 6, the start of it CdCr 2 S 4, other spin glasses and other systems Spinel B-site 15/20

16 Other Spin Glasses and other types of experiments Memory effect on the ZFC magnetization, Aging steps imprinted in zero field cooling : well defined dips in the difference with a reference curve without aging steps V. Dupuis, Ph. D, /20

17 Aging and scaling in disordered systems Fractal Colloidal gels Studied by dynamic light scattering L. Cipelletti et al, PRL 84 (2000) 2276 Studies in other disordered systems Colloids, gels and paste under constraint or not Age as the stop of the shear XPCS : X-ray photo-correlation spectroscopy on ferrofluids, V. Dupuis et al 17/20

18 XPCS on ferrofluids : translational dynamics X-ray beam from Silicon Mirror channel cut Si(111) 8keV pinhole guard-slit sample beamstop CCD sample stage D = 3300 mm R s 60 m «Dynamic Light Scattering with coherent X rays» Experimental setup of the ID10C end-station of the TROÏKA beamline at ESRF ID10C Digital Autocorrelator 2D-XPCS : recording speckle patterns with a CCD and computer treatment afterwards 18/20

19 XPCS on ferrofluids : translational dynamics Ferrofluids: d=11nm particules Aging dynamics and stretched exponential relaxations V. Dupuis, E. Wandersman, G. Mériguet, E. Dubois and R. Perzynski (Laboratoire des Liquides Ioniques et Interfaces Chargées, Jussieu) and A. Robert (ESRF) ξ 14 nm β 1.5 Speckle in ferrofluids 19/20

20 Miguel Ocio Thanks to J.M. Hammann, E. Vincent and V. Dupuis 20/20