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Experiments on the time dependence of the response function of a Ag(11 at%Mn) spin glass at a temperature below the zero field spin glass temperature are used to explore the non-equilibrium nature of the spin glass phase. It is found that the response function is only governed by the thermal history in the very neighbourhood of the actual measurement temperature. The thermal history outside this narrow region is irrelevant to the measured response. A result that implies that the thermal history during cooling (cooling rate, wait times etc.) is imprinted in the spin structure and is always retained when any higher temperature is recovered. The observations are discussed in the light of a real space droplet/domain phenomenology. The results also emphasise the importance of using controlled cooling procedures to acquire interpretable an...
Comment: EPL style; 7 pages, 5 figures
Reply to the Comment by L. Berthier and J.-P. Bouchaud, Phys. Rev. Lett. 90, 059701 (2003), also cond-mat/0209165, on our paper Phys. Rev. Lett. 89, 097201 (2002), also cond-mat/0203444
The diluted Ising antiferromagnet, Fe_{0.31}Zn_{0.69}F_{2}, has been investigated by dynamic susceptibility measurements in zero and and finite applied dc-fields. In zero field, there is a para- to antiferromagnetic phase transition at $T_{N} \approx {20.0 K}$, followed by a dramatic slowing down of the dynamics at low temperatures. The latter described by a pure Arrhenius law. The effect of a superposed dc-field on the antiferromagnetic phase transition and on the low-temperature dynamics is investigated, and a comprehensive static and dynamic phase diagram in the H-T plane is derived. In agreement with earlier results on the same system, $T_{N}(H)$ follows a random-exchange Ising model to random-field Ising model crossover scaling for fields $H \leq 1.5 T$. A random-field induced glassy dynamics appears for higher values of H, wher...
Non-equilibrium dynamics in an interacting Fe-C nanoparticle sample, exhibiting a low temperature spin glass like phase, has been studied by low frequency ac-susceptibility and magnetic relaxation experiments. The non-equilibrium behavior shows characteristic spin glass features, but some qualitative differences exist. The nature of these differences is discussed.
The magnetic and structural properties of oxygen-deficient perovskites with composition Ba3Fe2WO9-6 (BFWO) have been systematically studied for two different oxygen contents corresponding to delta = 0.00 and 0.55 in the chemical formula in order, to determine and correlate their chemical composition, structural and magnetic properties. The evolution of nuclear and magnetic structures with temperature has been investigated by neutron powder diffraction. It was shown that at room temperature the stoichiometric compound (delta = 0.00) adopts a hexagonal 6H-perovskite structure (space group P6(3)/mmc). This phase, when heated at high temperature under a stream of Ar gas, transforms to an oxygen-deficient phase delta = 0.55), which is an ordered cubic perovskite structure (space group Fm-3m). The crystallographic and magnetic properties of ...
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