Structural Analysis and Magnetic Properties of FeCo Alloys Obtained by Mechanical Alloying

Abstract

A systematic study on the structural and magnetic properties of Fe100-xCox alloys (10<x<90, Δx=10 in wt. percent) obtained by mechanical alloying is presented. Elemental powders of Fe and Co mixed in an adequate weight ratio were milled at room temperature in a shaker mixer mill using vials and balls of hardened steel as milling media with a ball : powder weight ratio of 12 : 1. The mixtures were milled for 3 h. The results show that, after milling, for almost all the composition (up to x=60), solid solutions based on bcc structures were obtained. For Co-rich alloys (x≥70), different phases were found, revealing the formation of a metastable intermetallic phase (FeCo, wairauite) together with fcc-Co and hcp-Co phases. The specific saturation magnetization increases by increasing Co content, reaching a maximum value of 225 emu/g for hcp-Fe70Co30, and then it shows a diminution up to 154 emu/g for bcc-Fe30Co70. All studied alloys (Fe100-xCox) present low coercivity, in the range from 0 to 65 Oe, which is lower than reported. The coercivity increases with the increment in Co, reaching a maximum of 64.1 Oe for Fe40Co60. After that, the coercivity falls up to 24.5 Oe for Co-rich alloys, which make them a very low coercive material.

FeCo@N‐Doped Nanoparticles Encapsulated in Polyacrylamide‐Derived Carbon Nanocages as a Functional Filler for Polyethylene System

“…However, according to Sanchez-De Jesus et. al., [44] for the FeCo alloys obtained by mechanical alloying, the coercive force varied in the range from 0 to 65 Oe, which is lower than in our study.…”

“…After that, the coercive force drops to 24.5 Oe for Co-rich alloys, which make them a very low coercive material. [44] In a study by Prakash Karipoth et al, [45] the saturation magnetization and the coercive force values for the flower-like Fe 50 Co 50 NPs with an average diameter of 130 nm were 186 emu/g and 440 Oe, respectively. The higher value of the coercive force is explained by the shape anisotropy of the flower-like particles.…”

High-Moment FeCo Magnetic Nanoparticles Obtained by Topochemical H2 Reduction of Co-Ferrites

“…The M-H loops for both H 2 -reduced samples were characterized by an increased M S and reduced H C . The saturation magnetization at 5 K reached values of ~203 Am 2 /kg and ~215 Am 2 /kg for the Fe 50 Co 50 and Fe 66 Co 34 MNPs, respectively, which were slightly lower than the values of FeCo bulk alloys of similar compositions [20]. This reduction was probably due to the formation of a thin oxide shell, which may have arisen at the intermediate step when the sample was transferred from the furnace to the glow box.…”

“…Among the family members, the Fe 100-x Co x intermetallic alloys show a distinctive combination of a high Curie temperature, low magneto-crystalline anisotropy, and high saturation magnetization, which reaches a maximum value of 240 Am 2 /kg in the Fe 65 Co 35 alloy [18][19][20]. Despite these interesting properties, FeCo particles are unstable in air and relatively difficult to synthesize with respect to magnetic oxide materials [21].…”

Magnetic Properties of Fe₁₋ₓCoₓSi Single Crystals at Low Co Impurity Concentrations

“…Thus, one can assume the presence of a ferromagnetic phase in the composition of the Fe 0,98 Co 0,02 Si sample. [17]. The Curie temperature of such an alloy is much higher than room temperature.…”