Magnetic properties of nickel carbide nanoparticles with enhanced coercivity

Abstract

Rhombohedral nickel carbide (Ni3Cx, x=0.7, 1.2 and 1.5) nanoparticles (∼ 110 nm) with enhanced magnetic coercivity (HC up to 1.3 kOe) at temperature below the spin-glass freezing (Tf) have been demonstrated. The presence of spin-glass state, which is seen at ∼17 K, is evident by the field dependence of the freezing temperature following the de Almeida-Thouless (AT) relationship and frequency dependence of Tf. Moreover, the spin-glass state is irreversible to the sweeping applied field and results in high HC at 10 K. With increases of the carbon content, we have found a gradual increasing trend in the saturation magnetization (MS: 6.6 to 9.2 emu/g) and coercivity (350 Oe to 1.3kOe) at 10 K. This is attributed to the increase of spin-glass contribution and the weak ferromagnetic phase.