Relaxation of thermo-remanent magnetization in different magnetic phases of Fe-rich γ-FeNiCr alloys

Abstract

The time decay of the thermoremanent magnetization(TRM) of the Fe 80−x Ni x Cr 20 (14 ≤ x ≤ 30) alloys has been measured for four different magnetic phases within the fcc γ-phase using a SQUID magnetometer. In the spin-glass phase(SG)(X=19) very distinct ageing effects are observed where M(t) can be described as M (t) = M 0 (t/t w ) −γ exp[−(t/τ ) 1−n ] for the entire time domain. In the reentrant spin-glass(RSG)(X= 23 and 26), M(t) can be better represented by the stretched exponential with an addition of a constant term which can be well explained by the Gabay-Toulouse(GT) model.We have also measured the linear and non-linear ac susceptibilities for the sample X=23 and confirmed the presence of the ferromagnetic(FM) ordering down to the lowest temperature. In the RSG(X=23), the TRM shows a minimum near T c and a local maximum just above T c . In the FM phase (X=30) the popular prediction of the power law decay of the TRM is observed. The latter is indistinguishable from the stretched exponential in the antiferromagnetic(AF) phase (X=14).

Investigations of the singlet ground state system: PrIrSi3

“…As seen from figure 5 the M (t) decays very slowly with time and remains nonzero even after 62000 s. A semilogarithmic plot of M (t) data is shown in the inset of figure 5 which clearly shows that M (t) data do not follow the logarithmic decay, M (t) = M 0 − S log(t). However, the M (t) data could be well fitted by a superposition of a stretched exponential and a constant term, [29,30] …”

Thermoremanent magnetization in Mn-richCu100−xMnx (x=Patel1, Kumar2, Majumdar3 2002Phys. Rev. B8060View full textAdd to dashboardCite

“…Very similar conclusions were reached in an antiferromagnetic FeNiCr alloy. 5 It should be noted here that all the three alloys in the present investigation have long-range-antiferromagnetic order. However, in an earlier work Ikeda and Kikuta 13 could not find any relaxation of TRM over a period of 10 h in the antiferromagnet Mn 0.45 Zn 0.55 F 2 for TϽT N .…”

“…Thermoremanent magnetization ͑TRM͒ in different magnetic phases has been recently summarized and studied in ␥ϪFe 80Ϫx Ni x Cr 20 (14рxр30) alloys showing antiferromagnetic, spin-glass, re-entrant spin-glass, and ferromagnetic phases as x is varied. 5 Several theoretical models have been discussed for the time dependence of magnetization ͑see Ref. 5 and references therein͒.…”

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“…(3) Power law relaxation M(t) = M 0 t −ζ , ζ < 1. This type of relaxation has been observed in spin glasses such as the γ -FeNiCr alloys [21] and in single-domain ferromagnetic nanoparticles [22]. This behavior can be understood in the context of the flipping of spin clusters [23].…”