اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدGrowth of a dynamical correlation length in an aging superspin glass
121
0
0.0
(
0
)
تأليف
Elie Wandersman
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report on zero field cooled magnetization relaxation experiments on a concen- trated frozen ferrofluid exhibiting a low temperature superspin glass transition. With a method initially developed for spin glasses, we investigate the field dependence of the relaxations that take place after different aging times. We extract the typical number of correlated spins involved in the aging dynamics. This brings important insights into the dynamical correlation length and its time growth. Our results, consistent with expressions obtained for spin glasses, extend the generality of these behaviours to the class of superspin glasses. Since the typical flipping time is much larger for superspins than for atomic spins, our experiments probe a time regime much closer to that of numerical simulations.
قيم البحث
اقرأ أيضاً
Effects of temperature changes on the nonequilibrium spin-glass dynamics of a strongly interacting ferromagnetic nanoparticle system (superspin glass) are studied. In contrary to atomic spin glasses, strong cooling rate effects are observed, and no e
vidence for temperature-chaos is found. The flip time of a magnetic moment is much longer than that of an atomic spin and hence much shorter time scales are probed within the experimental time window for a superspin glass than for an atomic spin glass. Within a real space picture the cumulative aging observed for the superspin glass can be explained considering that all investigated length scales are shorter than the temperature-chaos overlap length. The transient relaxation, observed in experiments after temperature changes, can be understood as the adjustment of thermally active droplets, which is mutatis mutandis the Kovacs effect observed in most glassy systems.
We present the experimental observation of the fluctuation-dissipation theorem (FDT) violation in an assembly of interacting magnetic nanoparticles in the low temperature superspin glass phase. The magnetic noise is measured with a two-dimension elec
tron gas Hall probe and compared to the out of phase ac susceptibility of the same ferrofluid. For intermediate aging times of the order of 1 h, the ratio of the effective temperature $T_{rm eff}$ to the bath temperature T grows from 1 to 6.5 when T is lowered from $T_g$ to 0.3 $T_g$, regardless of the noise frequency. These values are comparable to those measured in an atomic spin glass as well as those calculated for a Heisenberg spin glass.
A new protocol for an aging experiment is studied in the electron-glass phase of indium-oxide films. In this protocol, the sample is exposed to a non-ohmic electric field F for a waiting time t_{w} during which the system attempts to reach a steady s
tate (rather than relax towards equilibrium). The relaxation of the excess conductance dG after ohmic conditions are restored exhibit simple aging as long as F is not too large.
We investigate the relaxation process and the dynamical heterogeneities of the kinetically constrained Kob--Anderson lattice glass model, and show that these are characterized by different timescales. The dynamics is well described within the diffusi
ng defect paradigm, which suggest to relate the relaxation process to a reverse--percolation transition. This allows for a geometrical interpretation of the relaxation process, and of the different timescales.
The growth of the spin-glass correlation length has been measured as a function of the waiting time $t_{mathrm{w}}$ on a single crystal of CuMn (6 at.%), reaching values $xisim 150$ nm, larger than any other glassy correlation-length measured to date
. We find an aging rate $mathrm{d}ln,t_{mathrm{w}}/mathrm{d}ln,xi$ larger than found in previous measurements, which evinces a dynamic slowing-down as $xi$ grows. Our measured aging rate is compared with simulation results by the Janus collaboration. After critical effects are taken into account, we find excellent agreement with the Janus data.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
