xxiii πανελληνιο ÏƒÏ Î½ÎµÎ´ÏÎ¹Î¿ Ï†Ï ÏƒÎ¹ÎºÎ·Ï‚ στερεας καταστασης & επιστημης ...

Synthesis, Structural Characterization and Magnetic Properties of ZnFe 2 O 4 and Indoped
ZnFe 2 O 4 nanoparticles
M. Maletin 1,2 , E. G. Moshopoulou 1 , A. G. Kontos 3,4 , E. Devlin 1 , V. V. Srdic 2
1 Institute of Materials Science, NCSR «Demokritos», 15310 Agia Paraskevi, Greece
2 Department of Materials Engineering, Faculty of Technology, University of Novi Sad, Bul. Cara Lazara 1, 21000 Novi Sad,
Serbia
3 Physics Department, National Technical University of Athens, 15780 Athens, Greece
4 Institute of Physical Chemistry, NCSR «Demokritos», 15310 Agia Paraskevi, Greece
The spinel ZnFe 2 O 4 and doped derivatives intrigued solid state scientists for more than a century, since they exhibit a
complex relationship between preparation method, form (single-, poly- or nano- crystalline), doping, crystal and magnetic
structure and magnetic properties. Especially nanocrystalline ZnFe 2 O 4 and doped derivatives are attractive materials not only
from the fundamental point of understanding such a complex relationship but also for applications in such diverse fields as
energy, medicine and environment. Our contribution to this area of magnetism is to investigate the just-mentioned
relationship for nanoparticles of ZnFe 2 O 4 and In-doped ZnFe 2 O 4 with ultimate goal to design and produce new
electroceramics with novel or enhanced properties for specialized applications.
By using a co-precipitation method we produced single-phase ZnFe 2 O 4 and Zn 1-x In x Fe 2 O 4 (with nominal
composition x = 0.15) nanoparticles. They have size of about 4 nm deduced by conventional powder X-ray diffraction and
high resolution transmission electron microscopy. To our knowledge, this is among the smallest size’s single phase ZnFe 2 O 4
nanoparticles ever produced. For higher In-content, namely 0.2≤x≤0.6 (nominal composition), the spinel phase is present but
also a second highly crystalline phase, In(OH) 3 , is clearly observed by conventional powder X-ray diffraction. Ongoing
Mössbauer experiments reveal that there is disorder among the cations in the spinel structure for both undoped and In-doped
ZnFe 2 O 4 nanoparticles. Raman scattering measurements revealed that In-doping induces significant positive frequency shifts
of about 15 cm−1 for both A1g modes, demonstrating that In is indeed incorporated into the structure. The frequency shifts
observed are justified by the strong coupling of the oxygen atoms with In.
Magnetic measurements obtained by a SQUID magnetometer, revealed that In-doped ZnFe 2 O 4 nanoparticles are
paramagnetic at room temperature. At 5 K, the characteristic hysteresis loop has been obtained. The magnetization of the Indoped
ZnFe 2 O 4 nanoparticles decreases and their coercivity increases compared with undoped ones.
The above study reveals a complex structure-property relationship in spinel nanoparticles and advances our basic
understanding on the magnetism of nanoscale spinel systems. It also demonstrates that these materials are flexible and
adaptive to changes of the doping concentration and therefore they hold promises to be susceptible to processing and thus to
be useful for a wide variety of applications.
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