Synthesis and Magnetic Properties of CoO Nanoparticles

Abstract

Pure CoO nanoparticles in the 4.5-18 nm range have been prepared by the decomposition of Co(ΙΙ) cupferronate in Decalin at 270 °C under solvothermal conditions. The particles have been characterized by X-ray diffraction, transmission electron microscopy, and cognate techniques. The particles are stable because of the organic coating that occurs in situ. The organic coating is readily removed by heating the particles to 260 °C without loss of the nanoparticulate nature. Magnetic measurements reveal the presence of ferromagnetic interactions at low temperatures in the small CoO nanoparticles (<16 nm). The small nanoparticles do not exhibit a distinct antiferromagnetic transition around 300 K as the bulk sample but instead show hysteresis below a blocking temperature of ∼10 K.

Remanent magnetization in CoO antiferromagnetic nanoparticles

“…28. Briefly, 0.25 g of Co͑cup͒ 2 were added to 25 mL of octadecene and the mixture was sealed in a Teflon-lined stainless-steel autoclave.…”

Shape control of CoO and LiCoO2 nanocrystals

“…CoO nanocrystals with various sizes and morphologies have been synthesized via several chemical synthetic procedures [23][24][25][26][27], including the thermal decomposition of organometallic compounds such as Co 2 (CO) 8 [28], Co(II) cupferronate [29], and Co(acac) 3 (acac = acetylacetonate) [30] or metal-oleate complexes [31]. There have been fewer reports of LiCoO 2 nanocrystals with well-defined crystal morphologies due to the synthetic difficulties involved in preparing such materials [32].…”

The Co–Au interface in bimetallic nanoparticles: a high resolution STEM study

“…However, the interatomic distances measured for cobalt are not in agreement with the Co at bulk, but they are closer to those expected in cobalt oxide CoO. 24 This good agreement is apparent in Fig. 5b, where we have superimposed a ball-and-stick model of a fragment of the lattice of CoO.…”