Uniform Magnetic Chains of Hollow Cobalt Mesospheres from One‐Pot Synthesis and Their Assembly in Solution

Abstract

Magnetic chains up to 10 μm in length formed of hollow cobalt mesospheres (480–850 nm) with a 60 nm thick shell are synthesized by a new soft‐assembly protocol. The obtained chains show a saturation magnetization of 37.5 emu g–1, a remnant magnetization of 1.55 emu g–1, and a coercivity of ca. 66 Oe at 300 K. A possible mechanism for the formation of the chainlike hollow structures is proposed.

Anisotropy and magnetization reversal with chains of submicron-sized Co hollow spheres

“…No impurity phase such as the cobalt oxide or the precursor compounds have been detected. The structural analysis by high-resolution transmission electron microscopy (HRTEM) has also confirmed the hcp crystal structure [9]. Scanning electron microscopy (SEM) images of the sample are obtained by a JSM-5800, as shown in Fig.…”

“…In our previous works, we have reported the synthesis and characterization of uniform chains of Co hollow spheres [9] or Co hollow spheres with each cavity void enclosing a solid nanoparticle [10]. In the present paper, we report a study on the magnetic anisotropy properties for the chains of hcp Co hollow structure.…”

“…The sample has been characterized and presented in the previous report [9]. The major results are described as follows.…”

“…In the present paper, we report a study on the magnetic anisotropy properties for the chains of hcp Co hollow structure. The experimental details are presented in [9]. The blocking temperature obtained from the These values are one order smaller than the magnetocrystalline anisotropy, K 1 , of the bulk hcp Co, which is about 3 to 5 ×10 5 J/m 3 [11][12][13].…”

“…The preparation procedure and mechanism of synthesis are reported in [9]. In brief, the sample was synthesized by the reduction of CoCl 2 ·6H 2 O with hydrazine monohydrate in the presence of poly(vinylpyrrolidone) (PVP, Mw 58,000).…”