Mössbauer study of FeCoSiAlGaPCB amorphous alloys

Abstract

A Mössbauer spectrometry and magnetic study have been performed on FeCoSiAlGaPCB amorphous alloys in order to get information about the variations in the atomic short range order with the substitution of Fe by Co. The decrease of the Curie temperature with decreasing Fe content was analyzed in the framework of the molecular field theory. The average hyperfine magnetic field at 77 K decreases linearly with increasing Co content as does the average magnetic moment per transition metal atom and a linear dependence between both quantities is found. The standard deviation of the hyperfine magnetic field distribution at 77 K does not change with Fe substitution and the average isomer shift increases linearly with the Co content of the alloy. The hyperfine magnetic field distributions show a bimodal character that evidences the presence of two types of Fe environments in the as-cast alloys.

Mössbauer study of a Fe–Zr–B–Cu–(Ge, Co) nanocrystalline alloy series

“…These plots can be described as two overlapped peaks (bimodal behaviour): one, almost independent of the composition, is centred around 10 T, whereas the other peak maximum shifts from 17 to 27 T as Co content increases in the alloy. This bimodal character and a similar compositional dependence were also observed for other Co containing amorphous Fe-based alloy series [11,12]. The high H region of the distributions must be due to Fe surrounded by Fe and Co atoms, preferentially.…”

“…Although similar linear correlations have been reported for amorphous and crystalline alloys [11,20], it is worth noticing that, in this study, the linear correlation between <H> and < TM > is observed for systems with different amount of crystalline and amorphous phases, characterized by the value of X C . Figure 7 clarifies this point.…”

The influence of Co addition on the magnetocaloric effect of Nanoperm-type amorphous alloys

“…20 It is worth mentioning that, in contrast to this behavior, amorphous alloys with larger metalloid concentration exhibit a monotonous decrease of T C am with increasing Co content. [21][22][23] In the case of the studied alloys, Co addition leads to an increase of the ͉⌬S M pk ͉ value, unlike the observed behavior for the FeCoSiAlGaPCB alloy series, with larger metalloid content. 17 It has to be noted that an estimate of the error in ͉⌬S M pk ͉ is below 3%, which is below the differences observed for both samples.…”

“…The explanation of this influence of the metalloid content on T C am and ͉⌬S M pk ͉ should be ascribed to the change in the local environment of Fe and Co atoms and its effect on the exchange interaction between atoms. 23 The ͉⌬S M pk ͉ value of the Cocontaining Nanoperm-type alloy is ϳ50% larger than that of a Mo-containing Finemet-type alloy, with a comparable T C am , measured under the same experimental conditions, 14 while the Co-free Nanoperm-type alloy increases the peak entropy change by ϳ31% with respect to the same Finemet-type alloy. Comparing with the Fe 70 B 5 C 5 Si 3 Al 5 Ga 2 P 10 amorphous alloy, 17 the Co-containing alloy presents a comparable value of ͉⌬S M pk ͉, with the advantage of a peak temperature T pk , which is 100 K closer to room temperature for the alloy studied in the present work.…”

Glass-forming ability and soft magnetic properties of FeCoSiAlGaPCB amorphous alloys

“…This result can be mainly ascribed to the decrease of the exchange interaction between Co-Co pairs provoked by the presence of metalloid atoms. 29 The Curie temperature and the coercive field are affected by structural relaxation processes: 31 T C increases as the annealing temperature increases and H C decreases monotonically as the relaxation progresses. The lowest coercivity, H C (min), obtained after annealing the samples for 30 min at temperatures between 713 and 733 K, decreases as the Co and B content of the alloy increases ͓Fig.…”