MnCoSi-based alloys, as a new type of magnetically controlled functional alloys, have attracted much attention because of their rich magnetic structures[1] and excellent functional behaviors such as magnetocaloric, abnormal thermal expansion, and magnetostrictive. Considerable efforts have been devoted to developing high-performance MnCoSi-based alloys. To date, fully dense and textured MnCoSi-based alloys have been achieved by adjusting the thermal treatment process[2, 3]. The critical field of metamagnetic transition behavior can be substantially reduced by chemical doping and modification. To further improve the mechanical properties and magnetic response of MnCoSi-based alloys, it is still urgent to find a feasible strategy based on microstructure and texture optimization.

In the present work, [100] textured MnCoSi alloys were fabricated by slow-cooling thermal treatment. Microstructure and crystallographic characterization revealed that the textured MnCoSi alloy consists of three different oriented orthorhombic TiNiSi-type martensite variants with their a-axis lying in the cross-section of the rod-like MnCoSi alloy. A reversible giant negative thermal expansion of 9350 ppm with a broad temperature span of 350 K was obtained, due to the antiferromagnetic rearrangement[4]. For the stoichiometric MnCoSi alloy, giant reversible magnetostrictions as much as −5268 ppm at 300 K were achieved. By substitution of Si with Ge element, a linear magnetostrictive effect below 2 T was observed in the MnCoSi0.84Ge0.16 alloys[5], due to the low critical field and the barrier of the interfaces between the variants.

References

[1] B. Ding, et al., Adv. Funct. Mater., 2022: 2200356.

[2] Y.Y. Gong, et al., Acta Mater., 2015, 98: 113-118.

[3] Q.B. Hu, et al., Appl. Phys. Lett., 2018, 112(5): 052404.

[4] X. Hao, et al., J. Alloy. Compd., 2021: 161915.

[5] X. Hao, et al., Acta Mater., 2023, 242: 118486.