Authors
Abstract
In this study, a positron annihilation lifetime spectrometer was set up and its resolution was optimized. The spectrometer is a fast-slow arrangement with time resolution of 250 ps. To obtain lifetime components and their intensities from analyzing positron annihilation lifetime spectrum, the Pascual software is used. Positrons are from a source of radioactive 22NaCl with 20 μCi activity enclosed in 7μm thick Mylar foil. The source correction to lifetime components and their intensities were carried out though measurements on defect-free Aluminum samples and Mylar foils. The positron annihilation lifetime spectrum in nickel ferrite and iron oxide nanopowders were measured. The shortest component was attributed to the annihilation of nonlocalized positrons in the samples. The intermediate lifetime is due to annihilation of positron in octahedral and tetrahedral cationic vacancies in the spinel structure and to annihilation of positrons in the surface of nanoparticles and vacancy clusters. The longest component is attributed to the annihilation of orthopositronium atoms formed in the large free volumes in the intergranular regions of the nanoparticles through ‘‘pick-off” process.
Keywords
2. R Krause-Rehberg, and H S Leipner, “Positron Annihilation in Semiconductors: Defect Studies”, Springer-Verlag, Berlin Heidelberg (1999).
3. A Mukherjee, M Banerjee, S Basu, P M G Nambissan, and M Pal, Journal Of Physics D: Applied Physics 46 (2013) 495309.
4. Z Kargar, S M Asgarian, and M Mozaffari, Nucl. Instr. and Meth. B 375 (2016) 71.
5. F Selim, D Solodovnikov, M Weber, and K Lynn, Applied Physics Letters 91 (2007) 4105.
6. B Oberdorfer and R Würschum, Physical Review B 79 (2009) 184103.
7. J Čížek, I Procházka, M Cieslar, R Kužel, J Kuriplach, F Chmelík, I Stulíková, F Bečvář, O Melikhova, and R K Islamgaliev, Physical Review B 65 (2002) 094106.
8. E Tayebfard, A A Mehmandoost Khajeh Dad, M Khaghani, M Jafarzadeh Khatibani, and A M Poorsaleh, Iran. J. Phye. Res. 15, 1 (2015) 34.
12. S Chakrabarti, S Chaudhuri, and P Nambissan, Physical Review B 71 (2005) 064105.
13. S Chakraverty, S Mitra, K Mandal, P M G Nambissan, and S Chattopadhyay, Physical Review B 71 (2005) 024115.
14. P M G Nambissan, C Upadhyay, and H C Verma, Journal of Applied Physics, 93 (2003) 6320.
15. B Nasr, J Amighian, and M Mozaffar, Iran. J. Phye. Res. 6, 1 (2006) 49.
16. A Oorbafrani, P Kameli, and H Salamati, Iran. J. Phye. Res. 8, 3 (2008) 119.
17. M Nasr Isfahani and V Sepelak, Iran. J. Phye. Res 12, 3 (2012) 262.
18. A Bisi, G Gambarini, and L Zappa, Il Nuovo Cimento B 53 (1979) 428.
19. P Jain, S Bhatnagar, and A Gupta, Journal of Physics C: Solid State Physics 5 (1972) 2156.
20. F Becvár, J Cízek, and I Procházka, Acta Physica Polonica A 113 (2008) 1279.
21. F Bečvář, J Čížek, and I Prochazka, Applied Surface Science 255 (2008) 111.
22. T Troev and V Pavlov, Hyperfine Interactions 80 (1993) 999.
23. A V Thorat, T Ghoshal, J D Holmes, P M G Nambissan, and M A Morris, Nanoscale 6 (2014) 608.
24. P J Schultz and K G Lynn, Reviews of Modern Physics 60 (1988) 701.
25. J Smit and H P Wijn, “Ferrites-Physical Properties of Ferrimagnetic Oxides in Relation to Their Technical Applications”, N V Philip’s Gloeilampenfabrieken, Eindhoven, Holland, (1965).
26. M J Puska and R Nieminen, Reviews of Modern Physics 66 (1994) 841.
27. C Hübner, T Staab, and R Krause-Rehberg, Applied Physics A 61 (1995) 203-206.
28. H-E Schaefer, R Würschum, R Birringer, and H Gleiter, Physical Review B 38 (1988) 9545.
)