Controlling Magnetic-Field-Induced Shape Memory Response in Polycrystalline Off-Stoichiometry Fe47‑xMn24+xGa29 Microwires

TL;DR

This study explores how adjusting the composition of Fe–Mn–Ga microwires affects their magnetic shape memory behavior, enabling precise control for potential use in magnetic actuation and sensing.

Contribution

The paper introduces a composition-driven strategy to tune magnetic-field-induced shape memory effects in Fe–Mn–Ga microwires.

Findings

Fe45Mn26Ga29 microwires show a large thermal hysteresis width of 98 K due to Fe and Mn atom motion.

An antiferromagnetic transition shifts from 22 to 41 K depending on composition, linked to Fe and Mn 3d orbital interactions.

Abstract

The ferromagnetic shape memory (FSM) behavior of glass-coated
Fe47‑x
Mn24+x
Ga29 (x = 0–8 at. %) microwires has been
investigated
through temperature-dependent magnetization and ac magnetic susceptibility measurements. Magnetization measurements
as a function of temperature reveal an abrupt increase and decrease
in magnetization upon cooling and heating, respectively, indicating
characteristic thermal hysteresis (ΔT

hys
) behavior typically associated with a magnetic-field-induced
“diffusionless” martensitic transformation. The magnitude
and width of ΔT

hys
are strongly correlated with the Fe/Mn atomic ratio; notably, the
Fe45Mn26Ga29 microwire exhibits a
very large ΔT

hys
width of 98 K, which is attributed to local deformation involving
the motion of Fe and Mn atoms. Furthermore, an antiferromagnetic transition
is observed in a low-temperature region, shifting from 22 to 41 K
depending on composition. This shift is attributed to variations in
local exchange interactions arising from unequal occupation of Fe
and Mn 3d orbitals. These findings highlight a compositionally
driven design strategy that enables precise tuning of FSM behavior,
making Fe–Mn–Ga microwires promising candidates for
use in tunable magnetic actuation and sensing technologies.

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