Effect of Ni-doping concentration on structural, optical and magnetic properties of CdSe nanorods Jaspal Singh a,n , Sanjeev Kumar b , N.K. Verma a a Nano Research Lab, School of Physics & Materials Science, Thapar University, Patiala 147004, India b Department of Applied Sciences, PEC University of Technology, Chandigarh 160012, India article info Keywords: Nanorods Ferromagnetism Doping DMS abstract Cd 1x Ni x Se (x ¼0.00, 0.05, 0.10 and 0.15) nanorods have been synthesized using solvothermal route. X-ray diffraction (XRD) studies show that the nanorods possess wurtzite phase having hexagonal structure. Transmission electron microscopy (TEM) reveals the formation of nanorods having lengths 150–200 nm and diameters 10–15 nm. This has been further confirmed by high-resolution transmission electron microscopy (HRTEM) wherein lattice fringes corresponding to CdSe have been well observed. Reflectance measurements illustrate the red-shift in band gap with increase of Ni- doping concentration. Raman spectra display the shifting of longitudinal optical (LO) phonon modes, and modes activation due to doping in CdSe nanorods. Magnetic hysteresis (M–H) loops at room temperature reveal the ferromagnetism in nanorods. The saturation magnetization values have been observed to increase upto 10% due to carrier mediated exchange interactions, whereas a decrease has been observed for 15% Ni-doping concentration due to super-exchange interactions. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Dilute magnetic semiconductors (DMSs) are one of the functional materials having potential applications in the field of spintronics. The doping of transition metals (or rare earth elements) with partially filled d or f states paved the way for ferromagnetism in DMS materials [1,2]. Extensive work has been reported on various DMS systems such as ZnO [3], ZnS [4], ZnSe [5], CdS [6], and CdSe [7]. However, the origin of observed magnetism in DMSs is still contro- versial; low Curie temperature hinders their use for prac- tical device applications. Different mechanisms have been proposed but the explanation of double exchange, super- exchange and RKKY type interactions in DMS materials are still a topic of debate [8,9]. The presence of magnetic metal clusters, secondary phases, contaminants and intrinsic defects in DMS also give rise to the magnetism [10–12]. Xu et al. [13] reported the defect induced ferromagnetism in ZnO nanoparticles. They suggested that the defects are mainly related to oxygen vacancies which decrease with increase of particle size. Bogle et al. [14] also reported the crucial role of defects giving rise to magnetism in Co-doped CdS nanoparticles. Singh et al. [15] reported that F-center exchange interactions are responsible for the observed magnetism in Fe-doped CdSe nanorods. The trapped elec- trons (defects) due to charge imbalance between Cd 2 þ and Fe 3 þ ions in Fe doped CdSe nanorods give rise to the observed magnetism. However, a few reports are available on Ni-doped CdSe nanorods. As per our knowledge, Kumar et al. [16,17] group is the one who reported magnetism in Ni-doped CdSe nanostructures. In this paper, the effect of Ni doping on structural, optical and magnetic properties of CdSe nanorods, synthe- sized using solvothermal route, has been reported. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/mssp Materials Science in Semiconductor Processing http://dx.doi.org/10.1016/j.mssp.2014.03.032 1369-8001/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ91 0175 2393343. E-mail address: jaspal0314@gmail.com (J. Singh). Materials Science in Semiconductor Processing 26 (2014) 1–6