Suppression of martensitic transformation in Fe₅₀Mn₂₃Ga₂₇ by local symmetry breaking

Defects-induced local symmetry breaking has led to unusual properties in nonferromagnetic ferroelastic materials upon suppressing their martensitic transformation. Thus, it is of interest to discover additional properties by local symmetry breaking in one important class of the ferroelastic materials, i.e., the ferromagnetic shape memory alloys. In this letter, it is found that local symmetry breaking including both tetragonal nano-inclusions and anti-phase boundaries (APBs), suppresses martensitic transformation of a body-centered-cubic Fe₅₀Mn₂₃Ga₂₇ alloy, however, does not affect the magnetic ordering. Large electrical resistivity is retained to the low temperature ferromagnetic state, behaving like a half-metal ferromagnet. Lower ordering degree at APBs and local stress fields generated by the lattice expansion of tetragonal nanoparticles hinder the formation of long-range-ordered martensites. The half-metal-like conducting behavior upon suppressing martensitic transformation extends the regime of ferromagnetic shape memory materials and may lead to potential applications in spintronic devices.