Neutron and x-ray scattering studies of field-cooled orderingin the three-dimensional random-field Ising model

Abstract

We report a magnetic neutron and x-ray scattering study of the correlation length and order parameter of the random-field Ising magnets Fe 0.5 Zn 0.5 F 2 and Mn 0.45 Zn 0.55 F 2 on field cooling. Fitting the inverse correlation length, , measured above the metastability temperature, T M (H) in Fe 0.5 Zn 0.5 F 2 , at Hϭ5 and 6 T to a power law yields the exponent ϭ1.5Ϯ0.3 together with the equilibrium transition temperatures, T N (H), which are found to be well below T M (H). We also estimate ␥ϭ2.6Ϯ0.5 and ␥ϭ5.7Ϯ1 for the connected susceptibility, , and the disconnected susceptibility, dis , exponents, respectively. The x-ray data reveal a long range ordered component coexisting with short range magnetic order in the field-cooled state, for weak random fields in both samples. The nucleation of the long range order occurs below T M (H). The intensity of the long range order component decreases with increasing field.

Full reduction of large finite random Ising systems by real space renormalization group

“…Also, our result for γ is in good agreement with the results of Refs. [11,19,22,26,27], while our result for ν is in good agreement with the results of Refs. [23,25,27,28,29].…”

“…[11,19,22,26,27], while our result for ν is in good agreement with the results of Refs. [23,25,27,28,29]. In Fig.…”

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“…Therefore the system can be thought of as effectively having a discrete symmetry and properties similar to model magnetic systems in the presence of random fields. 43 The presence of a stronger cubic anisotropy in PMN-60PT in comparison to PMN is further reflected in the slopes of the TO 1 and TO 2 modes. In PMN, the slopes ͓as defined by ប 2 ␣ in Eq.…”

Equilibrium Random-Field Ising Critical Scattering in the AntiferromagnetFe0.93Zn0.07F2Slanic1, Belanger2, Fernandez-Baca3 1999Phys. Rev. Lett.579680View full textAdd to dashboardCite

“…In contrast, Feng, et al [26] obtain ν = 1.5 ± 0.3, γ = 2.6 ± 0.5 andγ = 5.7 ± 1.0 for F e 0.5 Zn 0.5 F 2 . This discrepancy, however, may be the result of the analysis of data which may lie below T eq (H), where hysteresis prevents a study of the equilibrium critical behavior.…”