Selective Synthesis of Peapodlike Ni/Ni₃S₂ Nanochains and Nickel Sulfide Hollow Chains and Their Magnetic Properties

Abstract Peapodlike Ni/Ni₃S₂ chains of about 30 nm in outer diameter, with Ni cores of 10–15 nm, can be synthesized by a sacrificial template route. The Ni₃S₂ shell exhibits paramagnetic properties with a mass susceptibility of χ ≈ 5 × 10⁻⁵ emu (gOe)⁻¹, while the ferromagnetic Ni cores show a superparamagnetic behavior with a blocking temperature of T_B ≈ 130 K. The shape anisotropy of the chainlike structure is determined as 5.0 × 10⁴ J·m⁻³, which is larger than the bulk magnetocrystalline anisotropy by one order of magnitude. The demagnetization factor is determined as ΔN = 0.29. The sample provides an ideal structure for studying the magnetization reversal property by the chain‐of‐sphere model. The observations on the formation of the peapod structure verify a growth mechanism of the nanoscale Kirkendall effect. Based on the preparation of peapod chains, a series of nickel sulfide hollow chains with average diameters of 25, 50, and 100 nm are fabricated. In addition, the phase transition for hollow chains from Ni₃S₂ to NiS is studied.