Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

Abstract

High-entropy alloys (HEAs) containing multiple principle alloying elements exhibit unique properties so they are currently receiving great attention for developing innovative alloy designs. In FeCoNi-based HEAs, magnetic behaviors strongly depend on the addition of alloying elements, usually accompanied by structural changes. In this work, the effect of non-magnetic components on the ferromagnetic transition and magnetic behaviors in equiatomic FeCoNiCrX (X=Al, Ga, Mn and Sn) HEAs was investigated. Alloy ingots of nominal compositions of HEAs were prepared by arc melting and the button ingots were cut into discs for magnetic measurements as functions of magnetic field and temperature. The HEAs of FeCoNiCrMn and FeCoNiCrSn show typical paramagnetic behaviors, composed of solid solution FCC matrix, while the additions of Ga and Al in FeCoNiCr exhibit ferromagnetic behaviors, along with the coexistence of FCC and BCC phases due to spinodal decomposition. The partial phase transition in both HEAs with the additions of Ga and Al would enhance ferromagnetic properties due to the addition of the BCC phase. The saturation magnetization for the base alloy FeCoNiCr is 0.5 emu/g at the applied field of 20 kOe (TC = 104 K). For the HEAs of FeCoNiCrGa and FeCoNiCrAl, the saturation magnetization significantly increased to 38 emu/g (TC = 703 K) and 25 emu/g (TC = 277 K), respectively. To evaluate the possibility of solid solution FCC and BCC phases in FeCoNiCr-type HEAs, we introduced a parameter of valence electron concentration (VEC). The proposed rule for solid solution formation by the VEC was matched with FeCoNiCr-type HEAs.

Magnetic properties of the complex concentrated alloy system CoFeNi0.5Cr0.5Alx

“…Comparing the calculated Curie Temperature with those found in literature 7,13 , it lies within the CoFeNiCr x system, where for x = 0.9 and 0.7 the T c = 300 and 200 K respectively. Kormann et al 's 8 theoretical calculations shows that M s experiences a 68% increase from 0.55 to 0.93 μB (54-91 Am 2 /kg) in CoFeNiCr x on Cr x reduction from x = 1 to x = 0.5 and an increase in T c from 119 to 418 K. However, Kormann's CoFeNiCr 0.5 -M s of 91 Am 2 / kg is higher than our synthesised n-Al 0 sample (58 Am 2 /kg, taken from M-H loop at 400 kA/m and 100 K) .…”

Semiconducting SiGeSn high-entropy alloy: A density functional theory study

“…The change of magnetism in HEAs depends on the included elements, which cause a structural change and the formation of a solid solution phase. Recent studies also indicate that the saturation magnetization at room temperature and the Curie temperature of HEAs are both tunable by controlling the concentrations of the principal elements [37]. As an example of the semiconducting properties of HEAs, recent studies found that upon successively adding alloying elements Ge, Pb, and Mn to the SnTe binary alloy to form HEAs, the valence bands and the band gaps in the HEAs are modified as a result of the cocktail effect [38].…”

Magnetic Characteristics of High Entropy Alloys

“…Moreover, they reported that for FeSiBAlNiCo HEAs annealing near re-crystallization temperatures was beneficiatial for the semi-hard magnetic characteristics. [37]. They reported that FeCoNiCrMn and FeCoNiCrSn exhibited paramagnetic behaviour.…”