Dislocation-Mediated Lattice Distortion and Griffiths Phase Behavior in Melt-Spun Ni₂MnSb Ribbons

The Griffiths phase, characterized by the persistence of local ferromagnetic clusters above the Curie temperature, is a key phenomenon in disordered magnetic systems. There are various mechanisms that can explain its formation, local lattice distortion in Heusler alloys is considered a very critical factor. In this work, the Ni₂MnSb ribbon samples were prepared by melt-quenching. The causes of local lattice distortion in the Ni₂MnSb ribbons were investigated, and their role in Griffiths phase formation was analyzed. Structural analyses reveal that increasing wheel speed progressively elevates dislocation density while enhancing local lattice distortions. Correspondingly, magnetic measurements demonstrate a systematic broadening of the Griffiths phase temperature range. Correlation of dislocation density, strain fields, and magnetic response establishes that dislocation-induced lattice distortions generate spatially inhomogeneous exchange interactions that stabilize ferromagnetic clusters within the paramagnetic matrix. This work not only offers a practical route for the controllable tuning of the Griffiths phase but also provides fundamental insight into the intrinsic mechanism underlying its formation in Heusler systems.