Coupling between phase transitions and glassy magnetic behaviour in Heusler alloy Ni 50 Mn 34 In 8 Ga 8

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Zhang, Le 
Lou, Xiaojie 
Zhou, Chao 
Ren, Xiaobing 

Abstract: The transition sequence in the Heusler alloy Ni50Mn34In8Ga8 has been determined from measurements of elasticity, heat flow and magnetism to be paramagnetic austenite → paramagnetic martensite → ferromagnetic martensite at ∼335 and ∼260 K, respectively, during cooling. The overall pattern of elastic stiffening/softening and acoustic loss is typical of a system with bilinear coupling between symmetry breaking strain and the driving structural/electronic order parameter, and a temperature interval below the transition point in which ferroelastic twin walls remain mobile under the influence of external stress. Divergence between zero-field-cooling and field-cooling determinations of DC magnetisation below ∼220 K indicates that a frustrated magnetic glass develops in the ferromagnetic martensite. An AC magnetic anomaly which shows Vogel–Fulcher dynamics in the vicinity of ∼160 K is evidence of a further glassy freezing process. This coincides with an acoustic loss peak and slight elastic stiffening that is typical of the outcome of freezing of ferroelastic twin walls. The results suggest that local strain variations associated with the ferroelastic twin walls couple with local moments to induce glassy magnetic behaviour.

Paper, Structure, dynamics and phase transitions, Heusler alloy, phase transitions, elasticity
Journal Title
Journal of Physics: Condensed Matter
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IOP Publishing
Engineering and Physical Sciences Research Council (EP/I036079/1)