Extended scaling in the magnetic critical phenomenology of the σ-phase Fe_0.53–Cr_0.47and Fe_0.52–V_0.48alloys

Abstract

The magnetization of the sigma-phase Fe(0.53)Cr(0.47) and Fe(0.52)V(0.48) alloys was studied as a function of temperature and field. The experiments show that both materials behave magnetically as re-entrant spin glass systems. Field versus temperature diagrams were obtained where the locations of the paramagnetic phase, the intermediate ferromagnetic-like phase and the spin glass fundamental state were displayed. These diagrams are in qualitative agreement with the predictions of the mean field theory for the interplay between the ferromagnetic and spin glass orderings. The critical phenomenology near the para-ferromagnetic transition could be investigated. It was found that the paramagnetic susceptibility is quite well described by the extended scaling scheme, where the reduced temperature is written as τ = (T - T(c))/T. The value obtained for the susceptibility critical exponent γ is intermediate between the prediction of the 3D Heisenberg universality class and the large values observed in spin glasses, as previously found in other re-entrant systems. The data do not confirm the validity of the extended scaling in the ferromagnetic-like phase. Using either the conventional or extended scaling protocols, the exponents β and δ were found to have values close to those reported for spin glass transitions. Despite the relevance of disorder and the anomalous values determined for β, γ and δ, the Widom scaling relation holds as an equality.

Magnetic phase diagrams in the H-T plane of the magnetically strongest sigma-phase Fe-V compounds

“…1. These values are slightly smaller than the value of 1.6 found previously for -FeV with x=48 and T C = 42 [25]. The values of T irr were defined as temperature of bifurcation in the Mcurves.…”

Evidence for a re-entrant character of magnetism of σ-phase Fe–Mo alloys: Non-linear susceptibilities

“…in all four cases the ground state is constituted by a spin glass (SG) which in the case of the Fe-Cr and Fe-V systems has a re-entrant character [11]. Some magnetic features revealed for  in the Fe-Re [9] and Fe-Mo systems [11,12] indicate that it also may be the case here. It is known that non-linear AC susceptibilities, 2, 3,…, can give a valuable information on the character of magnetism.…”

“…This finding is in line with our previous observations concerning the magnetism in other -phase binary alloys viz. Fe-Cr, Fe-V and Fe-Re [9,11].…”

The magnetism of σ-Fe54Cr46 alloy: AC and DC susceptibility studies

“…Its magnetism was, however, lately shown to be more complex than initially anticipated viz. in both cases it has a re-entrant character [9]. Furthermore, nuclear magnetic resonance measurements performed on r-FeV samples revealed that vanadium atoms present on all five sub lattices were magnetic [10].…”