Contents lists available at ScienceDirect Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm Research articles Fe 3 C nanoparticles for magnetic hyperthermia application A. Gangwar a , S.S. Varghese a , Sher Singh Meena b , C.L. Prajapat c,d , Nidhi Gupta c , N.K. Prasad a, ⁎ a Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India b Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India c Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India d Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India ARTICLE INFO Keywords: Iron carbide Nanoparticles Magnetic hyperthermia Heating ability ABSTRACT Fe 3 C magnetic nanoparticles were synthesized by solvothermal assisted technique. The X-ray and electron dif- fractions have confirmed the formation of monophasic iron carbide (Fe 3 C) nanoparticles. Transmission electron microscope analysis validated that the size of the particles was around 19–34 nm. The presence of only Fe and C in Fe 3 C was asserted by X-ray photoelectron spectroscopy (XPS). The room temperature Mössbauer spectroscopy also corroborates the occurrence of only this carbide phase. The saturation magnetization at ± 2 T and at 300 K was obtained to be around 88 Am 2 /kg with a coercivity of 17.3 mT and remanence of 6 Am 2 /kg. The oleic acid based ferrofluid of this carbide nanoparticles exhibited good heating ability in the presence of external alter- nating current (AC) magnetic fields. The optimum specific absorption rate and intrinsic loss power values were 85 W/g and 0.97 nHm 2 /kg at 23 mT and 261 kHz. Due to lack of reports on magnetic hyperthermia response for iron carbides, the values were compared with iron oxides. The values were found to be comparable. 1. Introduction Several forms of iron carbides such as Fe 3 C, Fe 5 C 2 , Fe 7 C 3 , Fe 2.2 C etc. are reported in the literature. Out of these carbides, Fe 3 C (cementite/ cohenite) has great technological importance [1,2]. This intermetallic compound has a stoichiometric composition of 6.67% carbon and 93.3% iron (Fe) by weight [3]. It has an orthorhombic crystal structure, high melting point (1837 °C), non-pyrophoric and strong magnetic (saturation magnetization, M S , for bulk ∼140 Am 2 /kg) behavior [4]. It is normally classified as a ceramic due to its high hardness and brit- tleness [1]. It is frequently found as an important constituent in ferrous metallurgy (in most steels and cast irons). The use of iron carbide during the production of steels and cast irons is remarkably environ- mental friendly because of its lowest C emission as compared to that of other virgin iron and steel making processes [5]. In addition, the iron carbide is much more effective and less costly than any other means to produce high-quality steel. This carbide can also be used as magnetic recording material due to its high magnetic strength and suitable Curie temperature (210 °C) [6]. The biomedical applications of magnetic nanoparticles (MNP S ) have become prominent topics for researches in the modern century. These applications are referred to as drug delivery, magnetic resonance ima- ging (MRI), magnetic hyperthermia treatment (MHT) etc. [7–9]. For such applications, the scientists have employed both ferromagnetic (metal/alloys e.g. Fe, FePt etc.) and ferrimagnetic nanoparticles (pure or substituted magnetite, Fe 3 O 4 or maghemite, γ- Fe 2 O 3 ) [10]. The former metallic materials though have higher M S values (∼220 Am 2 /kg for bulk Fe) but the toxic nature limits their suitability [7]. The en- capsulation of these metallic nanoparticles by the inert materials like platinum, gold, silver or silica etc. could enhance their compatibility but at the expense of enhanced size and reduced M S values [11]. Fur- ther, such nanolayer coatings are inhomogeneous, costly and tiresome to perform. In contrast, the magnetic iron oxides have adequate bio- compatibility and are being utilized with or without such coatings [12]. Nonetheless, these oxides have inferior M S values compared to that of the metallic ones (e.g. 90 Am 2 /kg for bulk Fe 3 O 4 ) [13]. In contrast, the iron carbide (e.g. Fe 3 C) found to display M S value considerably higher than that of its oxides counterpart and presumed to have better biocompatibility than metallic ones [14]. Due to its higher M S value, the actual materials required to get the therapeutic tem- perature (42–46 °C) during magnetic hyperthermia (MHT) treatment may be lesser than its oxide counterparts [15]. Further, the magnetic iron oxides found to get transformed into antiferromagnetic oxide with time in some of the carrier fluids [16]. Such conversion of iron carbide may not happen in fluids [17]. The synthesis route and the properties of iron oxide particles have been investigated to a large extent and thus there is less probability to get significant improvement in their prop- erties [18]. Hence, the researchers are looking for the other materials. https://doi.org/10.1016/j.jmmm.2019.03.028 Received 19 December 2018; Received in revised form 6 February 2019; Accepted 5 March 2019 ⁎ Corresponding author. E-mail address: nandkp.met@iitbhu.ac.in (N.K. Prasad). Journal of Magnetism and Magnetic Materials 481 (2019) 251–256 Available online 06 March 2019 0304-8853/ © 2019 Elsevier B.V. All rights reserved. T