Optical and magnetic properties of solid solutions of In 2x Mn x O 3 (0.05, 0.10 and 0.15) nanoparticles Sarvari Khatoon a , Kelsey Coolahan b , Samuel E. Lofland b , Tokeer Ahmad a,⇑ a Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India b Department of Physics and Astronomy, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA article info Article history: Received 30 May 2012 Received in revised form 7 August 2012 Accepted 8 August 2012 Available online 17 August 2012 Keywords: Nanostructured materials Chemical synthesis Optical properties X-ray diffraction Magnetic measurements abstract Mn-doped indium oxide (In 2x Mn x O 3 ) nanoparticles (7–12 nm) with x = 0.05, 0.10 and 0.15 have been synthesized by solvothermal method using oxalate precursor route for the first time. Powder X-ray dif- fraction studies showed the formation of monophasic cubic structure of In 2x Mn x O 3 solid solutions. X-ray diffraction and UV–visible reflectance studies revealed that Mn 2+ ions are doped into the In 2 O 3 lattice. Reflectance measurements showed red shift in an energy band gap which decreases with an increase in the Mn concentration. Maximum surface area of 768 m 2 g 1 is obtained for In 1.85 Mn 0.15 O 3 nanoparti- cles. Magnetization measurement revealed that all the samples are paramagnetic in nature with very weak antiferromagnetic interactions. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Dilute magnetic semiconductors (DMSs) have attracted consid- erable attention because of the possibility of incorporating charge and spin degrees of freedom in a single material, which results into a new class of devices known as spintronics [1–3]. In order to incorporate electronics, magnetics and photonics, it is mandatory to develop semiconductors that are not only ferromagnetic at room temperature but also have a tunable carrier density, large mobility, high magnetic moment and high optical transparency, which is likely to be used in devices for spin injection and detection. Tran- sition metal doped oxide semiconductors have shown immense interest in research because of the room temperature ferromagne- tism. Few of them belong to the transparent conducting oxide fam- ily, such as transition metal doped ZnO [4], TiO 2 [5], SnO 2 [6] and In 2 O 3 [7,8]. In 2 O 3 is a transparent n-type wide band gap semicon- ductor (3.7 eV) [9] with a cubic bixbyite crystal structure [10]. It has high mobility (10–75 cm 2 V 1 s 1 ) with a carrier density of 10 19 –10 20 electrons cm 3 . All these properties make In 2 O 3 the most promising candidate as host material for the development of transparent conducting ferromagnetic material. In recent years, few experimental reports are available in the literature on the room temperature ferromagnetism in transition metal doped In 2 O 3 , the transition metal includes Ti, V, Cr, Mn, Fe, Co, Ni and Cu [11–18]. The magnetic properties of these materials depend on several factors, such as substrate nature, synthesis technique and also on the oxygen vacancies [19,20]. Numerous physical tech- niques have been used for the synthesis of Mn-doped In 2 O 3 , such as, solid state route [13], pulsed laser deposition [14,15] and elec- tron beam evaporation technique [21]. More recently, Mn-doped In 2 O 3 nanopyramids have been synthesized by catalyst-free ther- mal process [22]. Recently, a theoretical study based on first- principle density functional theory showed that ferromagnetism can be enhanced by p-n codoping in Mn-doped In 2 O 3 dilute mag- netic semiconductors [23]. To the best of our knowledge, no re- ports are available in the literature for the chemical synthesis of Mn-doped In 2 O 3 nanoparticles. Chemists are more concerned on the theme to design and control the size of nanoparticles. The solvothermal method is one among the various low-temperature routes to tailor nanoparticles. Therefore, in this paper, we report the synthesis of Mn-doped In 2 O 3 nanoparticles using modified solvothermal method [24] through oxalate precursor route. Re- cently, this method was used for the synthesis of Ni-doped ZnO nanoparticles [25]. The term modified is used as we have carried out the synthesis in a simple refluxing glass assembly instead of an autoclave which is highly expensive. Using this method, we have obtained homogeneous nanoparticles of much smaller size with high surface area than those reports by other methods [13]. Although, these nanomaterials have been reported earlier by phys- ical methods but there are hardly any reports on their surface area study. Therefore, we have investigated their surface area studies at different Mn-concentrations and studied the variation with parti- cle size. Their optical and magnetic properties have also been stud- ied in detail. 0925-8388/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2012.08.038 ⇑ Corresponding author. Tel.: +91 11 26981717/3261; fax: +91 11 26980229. E-mail address: tahmad3@jmi.ac.in (T. Ahmad). Journal of Alloys and Compounds 545 (2012) 162–167 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom