High temperature structural and magnetic properties of cobalt nanowires

TL;DR

This study investigates the high-temperature structural and magnetic behavior of cobalt nanowires, revealing that their shape and properties are maintained up to 500 K, with reversible coercivity changes linked to anisotropy contributions.

Contribution

It provides detailed insights into the temperature-dependent magnetic and structural stability of cobalt nanowires using in situ XRD and SQUID measurements, highlighting the reversible and irreversible changes.

Findings

Structural and texture properties preserved up to 500 K

Coercivity decreases linearly with temperature due to anisotropy loss

Irreversible magnetic alterations occur above 525 K

Abstract

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 u0Hc=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.