Structural study of nanometric electrodeposited Co films using Co59 NMR

Abstract

A Co59 NMR experiment has been used to investigate the structure of two series of Co films with thicknesses varying from 5 to 400 nm which were electrodeposited on Cu at the electrolyte pH value of 2.1 and 3.7, respectively. It was shown that the overall structure of studied Co films consists of a very good quality fcc phase and a heavily faulted hcp phase in about equal proportions. The exceptions are very thin Co layers (below 20 nm) where the hcp structure was stabilized at pH 3.7 and overpotential of 0.9 V. This effect is attributed to the formation of hexagonal cobalt hydroxide in the early stage of deposition, which acts as a buffer layer stabilizing Co hcp structure.

Improving the Magnetic Properties of Co–CoO Systems by Designed Oxygen Implantation Profiles

“…The signal between the FCC and HCP-Co lines indicates the existence of stacking faults, which are stacking alterations of the atomic planes, in both Co phases. The low frequency tail in the NMR spectra originates from defects, such as grain boundaries, , and the interfaces with the Au buffer and the capping layer. Upon oxygen implantation, the amount of crystalline metallic Co significantly decreases because of the increased density of defects within the Co layer and due to the CoO formation.…”

C59oNMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

“…Internal field 59 Co NMR of ferromagnetic Co was first observed in 1959 by Gossard and Portis,7 and since then the application of internal-field NMR to ferromagnetic materials has developed considerably. [8][9][10] There has been an extensive subsequent use of 59 Co NMR to characterize the different Co atomic environments ͓fcc, hcp, and sfs͔ in Co metal, [11][12][13][14][15] in Co films, [16][17][18][19] in catalysts, 20,21 and in alloys. [22][23][24][25][26] However, the allotropic phase transformation of small Co particles has never been investigated by NMR spectroscopy.…”

A 59Co NMR study to observe the effects of ball milling on small ferromagnetic cobalt particles

“…Internal field 59 Co NMR of ferromagnetic Co was first observed in 1959 by Gossard and Portis [15], and since then the application of internal field NMR to ferromagnetic materials has developed considerably [16][17][18]. There has been an extensive subsequent use of 59 Co NMR to characterise the different Co atomic environments (fcc, hcp and stacking faults (sfs)) in Co metal [5,13,[19][20][21][22], in Co films [23][24][25][26], in catalysts [27,28] and in alloys [29][30][31][32][33]. Since the initial report of Gossard and Portis there has been some variation in the exact assignment of all the features of the 59 Co NMR spectra seen from such samples.…”