Moessbauer Studies of Metallic Ferromagnetic Glasses Under Pressure.
Abstract
The Mossbauer effect was used to study the pressure effects in the amorphous alloys (Fe-Ni-Cr)M, with x = 0.47, 0.40, 0.37 and 0.34, where M = (P,B,Si,Al) and. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). The Curie temperature (Tc) decreases linearly at low pressures, with. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). This decrease can be well described by the itinerant electron model. At high pressures, deviations were observed requiring analysis that takes account inhomogeneities. Mossbauer spectra showed that pressure decreases strongly their width. The effective field (Heff) decreases rapidly at low pressures, levels off at intermediary pressures (20 < P < 60 Kbars) decreasing again at higher pressures, due to influences from changes in Tc(P). (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). is concentration dependent. The ratio of the logarithmic pressure derivative of Heff(T) to that of Tc varies as. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). The pressure dependence of the width of the distribution of hyperfine fields showed that for x = 0.40 long range order is dominant. Correlations were also found between the half-width and the metalloids (M) concentration. The volume dependence of the average velocity shifts (S) showed that although for the low iron (x = 0.37 and 0.34). (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). it is > 1.0 mm/s in the other alloys. From comparison with the results of the pressure dependence of the isomer shift in the crystalline metals, it can be shown that the alloys with higher iron content have lower average nearest -neighbors. Study of the Mossbauer spectra of the crystallized samples pointed out similarities in the short-range order of amorphous and crystalline phases. Above Tc, the quadrupole splitting distribution was found broad extending over 1.0 mm/s. This distribution was also seen bimodal as in alloy (Fe-Ni)M with x = 0.40.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1981
- Bibcode:
- 1981PhDT.......167B
- Keywords:
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- Physics: Condensed Matter