Chemical and magnetic order in mass-selected large FeRh nanomagnets embedded in a carbon matrix

Guillermo Herrera (1) , Anthony Robert (1) , Véronique Dupuis (1) , Nicholas Blanchard (1) , Olivier Boisron (1) , Clement Albin (1) , Laurent Bardotti (1) , Damien Le Roy (1) , Florent Tournus (1) , Alexandre Tamion (1)

1 iLM - ENERGIE - iLM - Transport, Nanomagnétisme et Matériaux pour l'Énergie

In this paper, we present some specific chemical and magnetic order results obtained on bimetallic FeRh nanoparticles prepared under non-equilibrium conditions using mass-selected Low Energy Cluster Beam Deposition. Clusters around 7 nm incident diameter are in situ sandwiched between amorphous carbon films before transfer in air, with different surface coverage (from nearly isolated particles to percolating 2D films) in order to artificially increase diameters of the nanoparticles (NPs) by coalescence. On such FeRh@C samples, we observe different NPs morphologies and magnetic responses after UHV thermal treatments. By transmission electron microscopy (TEM), we show that after moderate annealing, nanoalloys evolved from a metastable structure towards the equilibrium CsCl-type (B2) chemically ordered phase with a more spherical shape. While from Superconducting Quantum Interference Device (SQUID) magnetometry measurements on 700 °C-annealed FeRh@C samples, we clearly evidence huge magnetization enhancement for such B2 nanoalloys with robust ferromagnetic (FM) signature even at very low temperature unlike their bulk counterparts.

Domaines: Physique [physics]

Guillermo Herrera, Anthony Robert, Véronique Dupuis, Nicholas Blanchard, Olivier Boisron, et al.. Chemical and magnetic order in mass-selected large FeRh nanomagnets embedded in a carbon matrix. European Physical Journal: Applied Physics, 2022, 97, pp.32. ⟨10.1051/epjap/2022210290⟩. ⟨hal-03679667⟩