Interdependence of microstructure, martensitic transformation, and magnetic behavior in Fe–Pd–Ga ferromagnetic shape memory ribbons toward functional tunability

Abstract Rapidly solidified Fe–Pd–Ga ferromagnetic shape memory ribbons, containing 1 and 3 at. % Ga, were obtained, and annealed at 950 °C for 15 and 30 min. Gallium substitution destabilizes the cubic lattice but preserves ferromagnetic order; thereby, it modifies phase stability and magnetic sensitivity. The combined effects of composition and heat treatment on microstructure, martensitic transformation temperatures, transformation heat, kinetics, and magnetic-field-induced transformation shift are presented. Magnetic sensitivity is evaluated using thermomagnetic and magneto-elastic measurements, being further validated through Clausius–Clapeyron analysis. Short-time heat treatment enhances structural relaxation and significantly increases the transformation heat, whereas prolonged annealing promotes grain growth and precipitate formation without suppressing thermoelastic behavior. Increasing Ga content results in a pronounced linear increase of the martensitic transformation temperature with magnetic field, from approximately 0.6 K T −1 for 1 at. % Ga to about 1.45 K T −1 for 3 at. % Ga. The good agreement between thermomagnetic measurements and Clausius–Clapeyron analysis confirms that the transformation shift is primarily governed by intrinsic thermodynamic parameters. The smaller magneto-elastic response indicates that microstructure limits strain expression. Therefore, functional control requires tuning the balance between intrinsic thermodynamic driving forces and microstructure-dependent magneto-elastic effects through composition and heat treatment. This enables the design of thermally adaptive and magnetically programmable materials, where 3 at. % Ga composition is suitable for active magnetic control and that of 1 at. % Ga is optimized for enhanced thermal stability and precision sensing.