Magnetic and Structural Properties of Mechanically Alloyed FexMn0.70?xAl0.30 (x = 0.40 and 0.45) Alloys

Abstract

Alloys of the system Fe x Mn 0.70--x Al 0.30 , x ¼ 0.40 and 0.45, prepared by mechanical alloying during 24, 48, 72 and 84 hours, were studied by X-ray diffraction, Mö ssbauer spectroscopy and ac magnetic susceptibility. The alloys with x ¼ 0.45 have a bcc structure for all the milling times whereas those with x ¼ 0.40 are bcc for 24 and 48 hours and bcc þ fcc for 72 and 84 hours. Mö ssbauer spectroscopy at room temperature shows that the alloys with x ¼ 0.40 are paramagnetic for all the milling times and their spectra were fitted with a doublet (bcc) for times of 24 and 48 hours and with a singlet (fcc) þ a doublet in the other cases. For the x ¼ 0.40 samples, by ac magnetic susceptibility measurements a reentrant spin-glass to ferromagnetic transition (RSG-F) was detected at low temperatures and a ferromagnetic to paramagnetic (F-P) transition at higher temperatures, whereas for the samples with x ¼ 0.45 only a superparamagnetic-like blocking process to ferromagnetic transition (SPM-F) was detected. Moreover, for both compositions, the ferromagnetic phase increases its stability with the milling time due to the increasing disorder induced by milling. The presence of the RSG phase is a consequence of the disorder and the competitive interactions, and presence of the SPM-like blocking process is due to the disorder and the increase of Fe content.

Glassy magnetism in mechanically alloyed FexCr90−xMn10 (x=18 and 35)

“…Between these transitions there is a plateau with relatively weak dependence of the susceptibility on the temperature. The plateau shown between these two transitions is typical of a re-entrant spin glass transition [19] and just has been detected for melt Fe-Cr-Mn alloys [7,8] and MA Fe 0.40 Mn 0.30 Al 0.30 alloys [12]. Then, in this case the low-temperature change of curvature can be attributed to the re-entrant spin glass to ferromagnetic phase transition and the high-temperature one to ARTICLE IN PRESS ferromagnetic to paramagnetic phase transition.…”

“…This method has been recently found to be capable of producing glassy magnetism. The presence of a spin-glass-like behavior in mechanically alloyed Fe 35 Cr 65 [9] and Fe 61 Re 30 Cr 9 [10] and re-entrant spin glass character in mechanically alloyed Cu 80 Fe 20 [11] and Fe 0.40 Mn 0.30 Al 0.30 [12] has been expressed in some recent works. However, few investigations were performed on ternary mechanically alloyed Fe-Cr-Mn alloys.…”

Local Structure and Magnetic Properties of Fe-Mn Nanocrystalline Alloys Fabricated by Mechanical Alloying Technique as a Function of Milling Time

“…MA is able to produce nanostructure materials with unique chemical, structural, electrical and magnetic properties, due to type of disorder created by the high density of defects and the small supersaturated solid solution, amorphous phases and nano powders, starting from a crystal size. Nowadays, MA has been used to prepare metastable phases such as mixture of elemental components or inter-metallic compounds [1][2][3][4][5].…”

“…Among these, LRO is frequently examined by X-ray diffraction studies while SRO could be examined by extended Xray absorption fine structure (EXAFS). EXAFS give useful information related to the local structure around specific atoms [4].…”

“…Various phenomena such as spin transition and shape-memory effect in Fe-Mn alloys have been reported [4,7]. In this work, we present preparation and characterization of the structure and magnetic behavior of Fe 50 Mn 50 alloys as changing the milling time.…”