Temperature dependent electron paramagnetic resonance (EPR) of SrZrO 3 Santosh K. Gupta a,n , Nimai Pathak a , P.S. Ghosh b , B. Rajeshwari a,b , V. Natarajan b , R.M. Kadam a a Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India b Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India article info Article history: Received 27 March 2015 Received in revised form 22 April 2015 Accepted 27 April 2015 Available online 28 April 2015 Keywords: SrZrO 3 Defect EPR Ferromagnetism abstract SrZrO 3 (SZO), a distorted perovskite was synthesized using gel-combustion route employing citric acid as a fuel and ammonium nitrate as oxidizer followed by characterization using X-ray diffraction (XRD) and electron paramagnetic resonance (EPR). Purity of the sample is confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Broadening and shift of the resonance field position in EPR spectrum to the lower field was observed as the temperature is lowered; which is the characteristic of ferromagnetic resonance spectra. The value of Curie–Weiss temperature obtained for SZO particles is 8.7 K. The positive sign of the Curie–Weiss temperature indicates that some of the spins are ferro- magnetically coupled in this sample. Theoretical investigation using density functional theory (DFT) calculation revealed that Vacancy at zirconium site contribute maximum to the magnetic moment. & 2015 Elsevier B.V. All rights reserved. 1. Introduction As quoted by Stolen et al. [1] perovskite structures have been termed an inorganic chameleon due to their large flexibility since the cubic mother structure easily distorts and adapts to the re- lative size of the ions forming the compound. The source of fas- cination is the diversity of the properties and their high sensitivity to crystal chemical tuning; i.e., a tiny change in chemical compo- sition or/and crystal structure may induce huge changes in che- mical and physical properties. Strontium zirconate (SZO), with chemical formula SrZrO 3 , is a complex oxide with a number of useful properties for device ap- plications. Its features include high temperature proton con- ductivity [2], a large dielectric constant [3], resistance switching [4,5], and ferroelectricity in artificial superlattices [6,7]. SZO crys- tallizes in the perovskite (ABO 3 ) structure, a class of compounds that is currently of significant research interest due to the emer- gence of novel interface phenomena [8,9]. Native points defects are known to play an important role in oxides and in many cases dominate the electronic and optical properties. For example, na- tive defects commonly act as carrier-compensation centers, in- troduce optically active states in the band gap [10,11], and are sometimes invoked as sources of free carriers [12]. Recently, there has been a great deal of interest in the study of magnetism in nonmagnetic semiconductors/insulator diluted with magnetic impurities due to possible applications in spin-based electronic systems [13]. However, there are controversies over the existence or absence of ferromagnetism in many of these materials [14]. Even if there is magnetism, the origin seems not to be in- trinsic to the main phase and possibly associated with magnetic impurity phases [15–17]. Room temperature d 0 ferromagnetism (FM) in pure semi- conductors or insulators without any ferromagnetism elements has attracted much attention in recent years. The experimental results have indicated that the observed room temperature FM originates from the oxygen vacancies for HfO 2 , CeO 2 , Al 2 O 3 , ZnO, In 2 O 3 , SnO 2 , TiO 2 and CuO films/nanograins [18–23], but from neutral cation vacancies for MgO films/nanograins [24–27]. Most of Ab initio calculations have demonstrated that neutral cation vacancies are responsible for the magnetic moment in oxides such as CaO, HfO 2 , TiO 2 , ZnO, SnO 2 , ZrO 2 and MgO [28–39]. The origin of magnetic moment in the nanoparticles of nonmagnetic materials was suggested to be due to cation or anion defects present at the surface of the particles. The nature of defect responsible for magnetism seems to depend on specific material. Conversely, the bulk samples obtained by sintering the nano- particles at high temperatures became diamagnetic. The magnet- ism in these nanoparticles has been suggested to be intrinsic and originates from cation or anion vacancies at the surfaces of na- noparticles depending on the nature of cations. In fact, the surface ferromagnetism has been envisaged to be a universal feature of Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2015.04.108 0304-8853/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Fax: þ91-22-25505151. E-mail address: santufrnd@gmail.com (S.K. Gupta). Journal of Magnetism and Magnetic Materials 391 (2015) 101–107