Mössbauer studies of ferromagnetic metallic glasses under high pressure

Abstract

An investigation of the Mossbauer effect in several ferromagnetic metalhc glasses at high pressure is reported. The amorphous alloys studied were of the form (Fe"Ni& ")M, where M is a combination of the metalloids P, 8, Si, or Al, and x varies from 0.34 to 0.47. In these materials the Curie temperatures were observed to decrease with pressure at a rate varying from -0. 16 to -0.50 K/kbar. Such behavior is consistent with the simpler itinerant models of ferromagnetism at low pressures, but deviates at the higher pressures, possibly due to inhoxnogeneities. The magnetic hyperfine spectra were analyzed by decomposing them into hyperfine field distributions, P(H). The average hyperfine fields and their pressure derivatives, qualitatively, behave similar to crystalline Fe-Ni alloys. Prom the behavior of the pressure dependence of the width of the distributions, one is able to draw some conclusions as to the short-range -versus -long-range nature of the magnetic interactions. The volume dependence of the isomer shifts in these materials suggests an inference as to the near-neighbor coordination of the iron atoms.

Tensile stress dependence of the Curie temperature and hyperfine field in Fe-Zr-B-(Cu) amorphous alloys

“…Under hydrostatic pressure, on the other hand, all bond lengths are shortened, and a different behavior of B HF should be expected. However, Bouzabata, Ingalls, and Rao on FeNiCr alloys 19 show a very similar behavior as that found here, ͗B HF ͘ decrease together with a narrowing of the distribution. This indicates that the effect of the changes in bond length on each atom is averaged over the different neighbors and the changes on the width of P(B HF ͒ reflect the existence of inhomogeneities or fluctuations in the alloys.…”

Influence of the short-range order on the magnetic properties of metallic glasses

“…Several works in the literature report a linear decrease of the isomer shift as a function of pressure; for example, in pure BCC Fe [33] (∂IS/∂(ln V ) = 1.33 mm s −1 ), and in Fe-Ni based metallic glasses [11], together with the simulations according to (5). [34]. Other authors [35] propose a model to describe the dependence of the isomer shift in binary Fe-B crystalline alloys based on structural considerations: coordination number of B around Fe (chemical effect) and the average distances between Fe-Fe pairs (topological term).…”

Pressure dependence of magnetic properties in Fe–Mn–B amorphous alloys: evidence for inhomogeneous ferromagnetism

“…A trend seems to emerge from these observations in that the pressure derivative of the saturation magnetization is much greater in case of amorphous alloys containing early transition-metal atoms (Mn in the present work) besides iron. A similar tendency might also be inferred from the more significant pressure dependence of the Fe hyperfine field (H eff ) in a Cr-containing alloy (d ln H eff (T)/dp = −0.10 GPa −1 for Fe 32 Ni 36 Cr 14 P 12 B 6 ) with respect to that of a Cr-free alloy (d ln H eff (T)/dp = −0.029 GPa −1 for Fe 27 Ni 53 P 14 B 6 ) [7]. However, for the lack of enough data, it is not yet clear if this feature is related to the 'early' type of the TM elements or it is associated with antiferromagnetic interactions observed in alloys with Mn and Cr.…”

“…However, only one report is known on the pressure variation of the saturation moment for amorphous alloys (Fe-Ni-P-B(-Si) alloy system [6]). Besides this early paper, the pressure dependence of the hyperfine field determined by Mössbauer measurements for some amorphous alloys [7][8][9] was used as a relevant quantity for comparison with the pressure dependence of saturation magnetization. The relation between the Fe atomic magnetic moment and hyperfine field for transition metal-metalloid type metallic glasses was established in [10] and revised recently [11].…”