Exploration of highly correlated Co‐based quaternary Heusler alloys for spintronics and thermoelectric applications

Abstract

Summary The half‐metallic character of new quaternary Heusler alloys CoXMnAs (X = Ru, Rh) is established along with their thermoelectric, mechanical, and thermodynamic properties. The optimization of energy suggests that alloys are stable in Y2‐type structure with a ferromagnetic character. The electronic band profile through generalized gradient approximation and modified Becke‐Johnson potential indicates the metallic character of alloys. However, with inclusion of Hubbard potential to generalized gradient approximation, the alloys depict half‐metallic character with semiconducting nature in spin‐down state. The alloys possess high magnetic moment, CoRuMnAs has 5 μB, whereas CoRhMnAs has 6 μB, following Slater‐Pauling rule MT = ZT − 24. The narrow band gap in spin‐down channel enhances the thermoelectric properties. The maximum value for thermopower (|S|) obtained is 44.3 and 53.44 μV/K for CoRuMnAs and CoRhMnAs, respectively. The variation of electrical conductivity, Seebeck coefficient, and figure of merit affirm increasing trend with temperature, which is a good indication of materials to be used in thermoelectric technology. The mechanical stability along with ductile nature of alloys is determined through elastic constants. Further, we have calculated thermodynamic properties and have established their dependence on temperature and pressure using quasi‐harmonic Debye model. The half‐metallic nature with efficient thermoelectric parameters strongly supports the possible application of alloys for spin devices and green energy generation.

Phonon phase stability, structural, mechanical, electronic, and thermoelectric properties of two new semiconducting quaternary Heusler alloys CoCuZrZ (Z = Ge and Sn)

“…Thus, in order to achieve high ZT, it requires very low thermal conductivity κ , and large Seebeck coefficient S , and electrical conductivity σ 4 . On comparing the results on S with those reported for CoRuMnAs and CoRhMnAs, we found that the maximum value of S , S max in our systems (lies in the range 26–28 μV/K) is less than that found in CoRuMnAs and CoRhMnAs 36 . However, various methods like carrier doping, nanostructuring, and chemical modification 61‐64 can enhance the TE performance of the materials.…”

“…For example, CoFeCrGe and CoFeTiGe were shown to exhibit figure of merit ZT value of 0.71 and 0.61, respectively 35 . In addition, a maximum value of thermopower │S│ of 53.44 μV/K (44.3 μV/K) was reported in CoRhMnAs (CoRuMnAs) 36 . Furthermore, Lin et al predicted a large Seebeck coefficient (539.20 μV/K at 300 K) and power factor (PF) (7 × 10 10 mW/mK 2 s at 300 K) in ZnFeTiSi 37 .…”

“…In particular, semiconducting half‐Heusler alloys are considered as important materials for energy production and spintronic applications 31 . In recent years, quaternary Heusler alloys (QHA) have received great attention particularly for their novel electronic structure, magnetic, and TE nature 32‐36 . For example, CoFeCrGe and CoFeTiGe were shown to exhibit figure of merit ZT value of 0.71 and 0.61, respectively 35 .…”

The significance of anti‐fluorite Cs 2 NbI 6 via its structural, electronic, magnetic, optical and thermoelectric properties

“…With the addition of PF, the thermoelectric efficiency was also deduced from the figure of merit (ZT = S 2 σT/κ) 63,64 . The depicted curve in Figure 9 shows that throughout all temperature regions ZT ranges from 0.00112 to 0.942.These values clarify that the Cs 2 NbI 6 can be efficiently used for thermoelectric purposes.…”

Current research and future prospective of cobalt‐based Heusler alloys as thermoelectric materials: A density functional approach

“…TE effect is designated as the reverse of squander heat into electrical energy that is, thermal‐to‐electric energy by using the Seebeck effect to make a way for sustainable energy technology and to overcome the energy crisis. Those materials, which convert heat energy into electrical energy, were called as TE materials 39,40 …”