Mossbauer and AC-susceptibility investigations of the alloy series FeAl_1-xMn_x

Abstract

Mossbauer and Ac-susceptibility measurementshave been carriedout on the alloy series FeAl,_,Mn, within the range 0.05 S x b 0.40. M6ssbauer spectra reveal the presence of electron charge density and magnetic hypefine field (BM) distributions at two iron sites. Thecharge density rises linearly with Mn concentration while B,,increases non-linearly with x indicating a polarized spin density of the itinerant electrons at the Fe nucleus due to the near neighbouring Fe and Mn magnetic moments. The onset of magnetism is explained by the formation of magnetic moment at the iron atom when AI atoms are removed and by the nearest neighbouring iron clustering. Magnetic measurements indicate the presence of mictomagneticclusters and show a transition from paramagneticstate tomagneticglass state for all the alloys. NO onset of ferromagnetism with increasing x was observed even at the concentration x = 0.4, in contrast to that observed in FeAI, $U, at a lower concentration x = 0.325. Comparison of the transition temperatures obtained from Mossbauer and ACsusceptibility measurements indicate relaxations of the magnetic clusters.

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

“…Theoretical calculations [2] based on a diluted and random-bond Ising model interpret this anomaly as due to a spin-glass (SG) behaviour. This hypothesis was experimentally confirmed by Kobeissi [3] who reported that the alloy with x ¼ 0.40 in the Fe 0.50 (Al 1--x Mn x ) 0.5 system presents a SG to P phase transition. By using both Mö ssbauer and magnetization techniques Pé rez Alcá zar et al [4] proved the presence of a reentrant spin-glass (RSG) phase in the Fe 0.45 Mn 0.30 Al 0.25 alloy.…”

“…Introduction Cast Fe-Mn-Al alloys in the bcc disordered phase have been highly studied from the theoretical and experimental point of view, due to the different magnetic phases that can appear as a consequence of the variation in composition and in temperature [1][2][3][4][5][6][7]. A preliminary work [1], performed at room temperature (RT), showed that the ferromagnetic (F) character of the alloys changes to a paramagnetic (P) one when the Al or Mn concentration increases.…”

Evidence of magnetic dipolar interaction in micrometric powders of the Fe50Mn10Al40 system: Melted alloys

“…These alloys are usually prepared according to the Chakrabarti method [44]. In the BCC structural phase, magnetic phases such us paramagnetic (P), ferromagnetic (F), antiferromagnetic (AF), spin-glass (SG) and reentrant spinglass (RSG) in the F and AF phases [45][46][47], respectively, were detected. Recently the pure and reentrant superparamagnetic (SP) phases were experimentally postulated [48,49] in this ternary Fe-Mn-Al system and a large effort is now in progress to understand this behavior.…”

Comparative study between melted and mechanically alloyed samples of the Fe50Mn10Al40 nanostructured system

“…These alloys have been generally prepared following the Chakrabarti method [1]. In the BCC structural phase the magnetic phase diagram presents behaviours like paramagnetic (P), ferromagnetic (F), antiferromagnetic (AF), spin-glass (SG) and reentrant spin-glass (RSG) in the F and AF phases [2][3][4], depending on both the concentration and the temperature. Recently, the pure and reentrant superparamagnetic (SP) phases were experimentally observed [5,6] in this alloy system.…”