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A study of the FM-AFM phase transition in FeRh : compositionally graded films and strain control

Mercredi 7 septembre 2016 10:30 - Duree : 2 heures
Lieu : Salle des séminaires - bât A - Campus CNRS, 25 rue des martyrs - 38000 Grenoble

Orateur : Soutenance de Thèse de Ba Doan NGUYEN

This thesis deals with the study and control of phase transition characteristics in magnetic films. In the case of FeRh-based magnetron sputtered films, the influence of both composition and strain were studied. Magnetic, structural and electrical characterization was made as a function of position on compositionally graded films. Addition of a third element (Pt or Ni) was used to shift the transition temperature. We established that a change in optical properties occurs in FeRh-based films on passing from the FM to AFM state. By studying the temperature dependent position of the optical transition, we were able to construct a phase diagram of the Fe-Rh-Pt system. Such a detailed phase diagram based on a continuous variation of composition, evidences an enhanced stability (higher transition temperature) of the AFM phase for a specific composition close to the equiatomic one. Strain control of the phase change in PMN-PT/FeRh heterostructures was investigated through transport measurements using set-ups developed in this thesis. The transition temperature could be shifted by up to 22 K upon application of a low electric field (10V ⇠ 0.32 kV/cm). The strain-induced resistance change is large, which is attractive for applications. The AFM state is stabilized in these anisotropically strained films. The anisotropic character of the piezo-electric strain plays a significant role compared to the isotropic volume change.

Contact : nora.dempsey@neel.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (Institut Néel)
Nature évènement : (Soutenance de thèse)
Site de l'évènement : Polygone scientifique

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