Gamma radiation roused lattice contraction effects investigated by Mo ssbauer spectroscopy in nanoparticle Mn–Zn ferrite P.P. Naik a , R.B. Tangsali a,n , S.S. Meena b , Pramod Bhatt b , B. Sonaye c , S. Sugur c a Department of Physics, Goa University, Taleigao Plateau, Goa 403206, India b Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085,India c Goa Medical College, Bambolim, Goa 403201, India HIGHLIGHTS  Nanoparticle Mn x Zn 1 x Fe 2 O 4 (x ¼0.4,0.5,0.6) samples were prepared and γ-irradiated.  Reduction of lattice constant and particle size observed as the consequences of γ-exposure.  Preferred existence of Fe in þ3 oxidation states.  Reduction in magnetic interaction between Fe ions due to Zn þ2 dilutions.  Permanent nature of radiation induced changes. article info Article history: Received 29 January 2014 Accepted 30 April 2014 Available online 10 May 2014 Keywords: Nanoparticles X-ray spectroscopy Gamma radiation Mo ssbauer spectroscopy Cation distribution abstract Nanopowders of Mn x Zn 1x Fe 2 O 4 with x ¼0.4, 0.5 and 0.6 were synthesized using a combustion synthesis method. X-ray diffraction (XRD) patterns obtained on samples confirmed formation of monophasic cubic phase material. Lattice parameters and X-ray densities were obtained from rietvield refinement of the XRD patterns. All samples were radiated with gamma radiation with a dose of 200 Gy obtained from 60 Co source. Structural and physical parameters, such as lattice constant, X-ray density and particle size, determined for as prepared samples (S A ) and gamma irradiated samples (S R ), showed extraordinary variations in their values. Saturation magnetizations (M S ), remnant magnetization (M R ) and coercive field (H C ) for both sets of samples illustrated an enhancement in their values for S R samples. Investigations were carried out using Mo ssbauer spectroscopy to divulge structural and magnetic information of all samples. Room temperature Mo ssbauer spectra were fitted with five magnetic sextets and a symmetric paramagnetic doublet for the data obtained on samples except for x ¼0.4, S A sample. The presence of well defined doublets in the spectra of S A and S R samples is attributes of super- paramagnetism, indicating the reduction in A–B superexchange interaction due to dilution of sub-lattice by Zn ions. Cation distribution at A site and B site, estimated from Mo ssbauer data exhibited amazing alterations which were highly stable. The variations in physical, structural and magnetic properties observed are attributed to change of Fe 2 þ /Fe 3 þ and Mn þ2 /Mn þ3 ratios in gamma-irradiated samples. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Nanoparticles of Mn–Zn ferrite with simple cubic structure are interesting because of their large number of innovative applica- tions in heat transfer devices, drug delivery systems, medical diagnostics, various sensor applications (Pankhrust et al., 2003; Tartaj et al., 2003; Mornet et al., 2004), as well as an exclusive opportunity they provide to understand both theoretically and experimentally the involvement of various interactions at nano- scale with emergence of fascinating properties, never observed in the past. Spinel ferrite has face centered cubic (fcc) structure in which oxygen atoms are cubic close packed in which two inter- stitial A-(tetrahedral) and B-(octahedral) sites are occupied by metal cations. If the metal ions M þ 2 occupy only tetrahedral sites then the spinel is a direct ferrite. If it occupies only octahedral sites then the spinel is an inverse ferrite. The tetrahedral and octahedral sublattice magnetizations are antiparallel and therefore a non-compensated magnetic moment occurs resulting in the ferrimagnetic structure. Mn–Zn ferrite is a magnetic material exhibiting excellent properties such as high permeability, high saturation magnetization, high resistivity, low power loss and superparamagnetism depending on the particle size of the material Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/radphyschem Radiation Physics and Chemistry http://dx.doi.org/10.1016/j.radphyschem.2014.04.038 0969-806X/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. E-mail address: rbtangsali@unigoa.ac.in (R.B. Tangsali). Radiation Physics and Chemistry 102 (2014) 147–152