Magnetostructural martensitic transformations with large volume changes and magneto-strains in all-d-metal Heusler alloys

TL;DR

This paper reports the development of all-d-metal Mn2-based Heusler alloys exhibiting large magneto-strains and volume changes due to magnetostructural martensitic transformations, promising for multi-field applications.

Contribution

It introduces new Mn2-based Heusler alloys with significant magneto-strain and volume change, highlighting the role of Co and Ti in tuning transformation temperatures and properties.

Findings

Large magneto-strain of 6900 ppm observed.

Volume change of -2.54% detected.

Martensitic transformation confirmed by XRD and HRTEM.

Abstract

The all-d-metal Mn2-based Heusler ferromagnetic shape memory alloys Mn50Ni40-xCoxTi10 (x = 8 and 9.5) are realized. With a generic comparison between d-metal Ti and main-group elements in lowering the transformation temperature, the magnetostructural martensitic transformations are established by further introducing Co to produce local ferromagnetic Mn-Co-Mn configurations. A 5-fold modulation and (3, -2) stacking of [00 10] of martensite are determined by XRD and HRTEM analysis. Based on the transformation, a large magneto-strain of 6900 ppm and a large volume change of -2.54% are observed in polycrystalline samples, which makes the all-d-metal magnetic martensitic alloys of interest for magnetic/pressure multi-field driven applications.