Low band gap Co 80 Ni 20 @RGO nanocomposite Debajyoti De 1,2,a , Subham Majumdar 2 and Saurav Giri 2 1 NITMAS, Diamond Harbor Road, 24 PGS (s), W.B., India 2 Dept. of Solid State Physics, Indian Association for the Cultivation of Science, Kolkata – 32, W.B., India a sspdd@iacs.res.in Keywords: Graphene, Nano alloy, Co 80 Ni 20 , RGO Abstract. We report a novel approach of designing ordered arrangement of disorder on the extended structures of graphene. We prepared single phase nanoparticles of Co 80 Ni 20 alloy embedded in Reduced Graphene Oxide (RGO). Co 80 Ni 20 shows a large moment and a soft ferromagnetic character like permalloy at room temperature. Temperature dependence of permittivity shows a behavior quite contrary to usual ceramic materials showing an increase with decreasing temperature, exhibiting a maximum. A very large magnitude of permittivity ~ 5000 is observed, which is possibly related to an interesting Maxwell-Wagner type effect arising from the charge localization in the graphene sheets. For a deeper insight of the mechanism, correlations with other phenomena are studied through magnetization, dc resistivity, I-V etc. investigations. Temperature dependent magnetization indicates toward strong ferromagnetic interaction and MH loop shows low coercivity ferromagnetic interaction at 4 K and even at room temperature. Introduction Graphene has been focused as an emerging candidate for future generation electronics. The hindrance is a very low band gap and low resistivity. Attempts to overcome this problem include sophisticated fabrication aiming to introduce controlled disorder driven by defects, which leads to localization of conductivity and opening of band gap between conduction and valence bands paving the way for novel graphene based materials. Although a lot has been investigated on graphene based materials regarding electronic or electrical behavior, very less is studied on the dielectric nature of such systems. Graphene, a two dimensional monoatomic thick building block of a carbon allotrope, has attracted appreciable attention due to its exceptional electronic and optoelectronic properties [1- 3]. Up to now various techniques are developed to synthesize thin sheets of graphene, of them chemical reduction route with hydrazine and ammonia is considered to be the most economical and effective method for large scale production of graphene nano sheets (GNs) [3-9]. Here, we report synthesis and characterisation of Co 80 Ni 20 alloy grown in Reduced Graphene Oxide (RGO). We want to concentrate our study on change in magnetic and electric properties when single phase alloy of Co 80 Ni 20 is embedded in two dimensional graphene sheets. Graphene sheets were prepared following reduced Hummers’ method [10]. We tried to develop a composite of Co 80 Ni 20 @RGO with weight percentage 3:1 or volume fraction φ=30%. 2 g of graphite powder was vigorously stirred with 1 g sodium nitrate and 50 ml concentrated sulphuric acid in an ice bath. 6 g KMnO 4 was added slowly keeping the temperature of the solution below 10 o C. Then the solution was brought to 80 o C with adding some warm water. After 1 h H 2 O 2 (30%) was added which created huge inflammation. The bright yellow solution was centrifuged in speed 6000 r.p.m. for 10 minutes after adding some HCl to eliminate the metallic impurities. Product was washed with distilled water and dried in 50 o C for some days and thus graphene oxide (GO) was formed. GO powder, desired amounts of cobalt chloride and nickel chloride were dispersed in ethylene glycol by sonication for several hours until the solution reaches homogeneity. Then appropriate amount of hydrazine hydrate (N 2 H 4 , 35%) was added and reaction was continued for 6 h at 80 o C with constant refluxing with cold water. The solution was centrifuged with speed 6000 r.p.m and calcined at 600 o C for 6 h under the flow of Ar (95%) and H 2 (5%). Thus the product was obtained where alloy is formed in Advanced Materials Research Vol. 856 (2014) pp 299-303 Online available since 2013/Dec/06 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.856.299 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 27.251.39.84-10/12/13,06:05:13)