Investigation on magnetic properties of mechanically alloyed τ-MnAlC with Fe addition

Abstract

The influence of Fe addition on thermal stability, crystallography, and magnetic properties of τ-Mn51Al47C2 was investigated. Alloys with composition 0.5,1,2,and 4) were synthesized by mechanical alloying method. High purity of τ-Mn(Fe)AlC up to 98% could be obtained after 10h of milling, then annealed at 1050 o C for 1h, and followed by an aging process at appropriate temperatures from 515 to 540 o C for 50 minutes. It was found that the thermal stability of both ε and τ phases was enhanced by the addition of Fe up to 4 at.% into MnAlC alloy through a shifting of ε-to-τ transformation temperature to high temperature region and a reduction in c/a ratio of Fe doped τ-MnAlC compared to iron free τ-MnAlC. While the magnetization and Curie temperature of Fe doped τ-MnAlC showed a reduction compared to iron free τ-Mn51Al47C2, coercivity seems not to be significantly affected.Ab initio calculation showed a lower magnetic moment of Fe (µFe = 1.77 µB) compared to Mn (µMn_average = 2.36 µB) in τ-Mn(Fe)AlC when Fe substituted Mn position at 1a site.

Investigation of Mn-Fe magnetic interaction in mechanically alloyed Fe doped-MnAlC by 57Fe Mössbauer spectrometry

“…The reason for the decline of magnetization was attributed to the reduction of its lattice parameters as the distance between neighboring Mn atoms greatly affects their magnetic interaction according to Bethe Slater curve [8]. However, as mentioned in our previous report [4], the Fe atom has its own magnetic moment and how it interacts with Mn atoms also contribute to the overall magnetic properties of the material. So far, only one theoretical study was carried out by Manchanda et al based on density functional theory (DFT).…”

“…The β and γ 2 are different in composition because it is easy to get high purity at those compositions. One can find the procedure of mechanical alloying method to make the ε and τ-Mn 50.5 Fe 0.5 Al 47 C 2 phases in [4]. The τ-Mn 50.5 Fe 0.5 Al 47 C 2 was achieved by secondary heat treatment at 525 o C for 50 minutes of the ε-Mn 50.5 Fe 0.5 Al 47 C 2 .…”

“…However, in τ-MnAl(C) crystal structure, like other tetragonal magnetic materials, there is a non-magnetic layer of Al atoms at 1d site, that does not contribute to its overall magnetic performance, and around 4 at.% of Mn atoms that enter the 1d site, having antiferromagnetic interaction with Mn atoms in the surrounding of the 1a sites [4]. Effort has been done to replace that layer by 3d transition metals in order to improve the magnetization of τ-MnAl(C) [5][6][7].…”

“…Effort has been done to replace that layer by 3d transition metals in order to improve the magnetization of τ-MnAl(C) [5][6][7]. In our previous work, doping Fe into τ-MnAl(C) was carried out in order to investigate the influence of Fe addition on the crystallography and magnetic properties of mechanical alloyed τ-MnAlC [4]. Although the magnetic performance was not improved, enhancement in thermal stability of bulk τ-MnAlC was obtained [4], which is beneficial for application of magnetic materials.…”

“…In our previous work, doping Fe into τ-MnAl(C) was carried out in order to investigate the influence of Fe addition on the crystallography and magnetic properties of mechanical alloyed τ-MnAlC [4]. Although the magnetic performance was not improved, enhancement in thermal stability of bulk τ-MnAlC was obtained [4], which is beneficial for application of magnetic materials. The reason for the decline of magnetization was attributed to the reduction of its lattice parameters as the distance between neighboring Mn atoms greatly affects their magnetic interaction according to Bethe Slater curve [8].…”