High temperature structural and magnetic properties of cobalt nanorods

Kahina Ait Atmane (1) , Fatih Zighem (2, 3) , Yaghoub Soumare (1) , Mona Ibrahim (4) , Rym Boubekri (4) , Thomas Maurer (3) , Jeremie Margueritat (1) , Jean-Yves Piquemal (1) , Frédéric Ott (3) , Gregory Chaboussant (3) , Frédéric Schoenstein (2) , Noureddine Jouini (2) , G. Viau (4)

1 ITODYS (UMR_7086) - Interfaces, Traitements, Organisation et Dynamique des Systèmes
2 LSPM - Laboratoire des Sciences des Procédés et des Matériaux
3 LLB - UMR 12 - Laboratoire Léon Brillouin
4 LPCNO - Laboratoire de physique et chimie des nano-objets

We present in this paper the structural and magnetic properties of high aspect ratio Co nanoparticles (~10) at high temperatures (up to 623 K) using in-situ X ray diffraction (XRD) and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. The coercivity can be modelled by µ0HC = 2(KMC + Kshape)/MS with KMC the magnetocrystalline anisotropy constant, Kshape the shape anisotropy constant and MS the saturation magnetization. HC decreases linearly when the temperature is increased due to the loss of the Co magnetocrystalline anisotropy contribution. At 500K, 50% of the room temperature coercivity is preserved corresponding to the shape anisotropy contribution only. We show that the coercivity drop is reversible in the range 300 - 500 K in good agreement with the absence of particle alteration. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation.

Mots clés: nanorods; cobalt; polyol process; permanent magnets; thermal treatments

Domaines: Matériaux

Kahina Ait Atmane, Fatih Zighem, Yaghoub Soumare, Mona Ibrahim, Rym Boubekri, et al.. High temperature structural and magnetic properties of cobalt nanorods. Journal of Solid State Chemistry, 2013, 197, pp.297. ⟨10.1016/j.jssc.2012.08.009⟩. ⟨hal-00916597⟩