caa a22 4500 445381558 CHVBK 20180317143019.0 cr unu---uuuuu 170323e20110101xx s 000 0 eng 10.1007/s10948-010-0943-1 doi (NATIONALLICENCE)springer-10.1007/s10948-010-0943-1 Exchange Bias, Memory and Freezing Effects in NiFe2O4 Nanoparticles [Elektronische Daten] [K. Nadeem, H. Krenn] Single-phase NiFe2O4 nanoparticles embedded in SiO2 matrix have been synthesized by sol-gel method. Average particle size lies in the range 8-12 nm. Magnetic measurements are taken by SQUID-magnetometer with a maximum applied field of ±7 T and temperature down to 4.2 K. An exchange bias effect in nanoparticles is due to the existence of strong core-shell interactions and it vanishes as the particle size decreases (<4nm). Spin disorder and frustration appear at the core-shell interface due to broken bonds on the surface. We have observed the exchange bias effect via hysteresis loop shift, when the sample is cooled in an applied field of 5T. In both AC and DC fields, our system exhibit memory effects at the halted temperatures. Furthermore, a sharp increase of coercivity at low temperatures (<50 K) is observed, which is attributed to increased surface anisotropy at low temperatures. For saturation magnetization vs. temperature data, Bloch's T 3/2 law (M(T)=M(0)⋅(1−BT b)) is fitted well and yields: B=4×10−05 K−3/2 and b=1.53. All these measurements prove the presence of exchange bias (core-shell interactions), memory effects, validation of Bloch's T 3/2 law and freezing effects in nickel ferrite nanoparticles dispersed in SiO2 matrix. Springer Science+Business Media, LLC, 2010 Ferrite nanoparticles nationallicence Core-shell nationallicence Spin-glass nationallicence SQUID-magnetometry nationallicence Nadeem K. Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, 8010, Graz, Austria aut Krenn H. Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, 8010, Graz, Austria aut Journal of Superconductivity and Novel Magnetism Springer US; http://www.springer-ny.com 24/1-2(2011-01-01), 717-720 1557-1939 24:1-2<717 2011 24 10948 https://doi.org/10.1007/s10948-010-0943-1 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10948-010-0943-1 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Nadeem K. Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, 8010, Graz, Austria aut NATIONALLICENCE 700 1- Krenn H. Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, 8010, Graz, Austria aut NATIONALLICENCE 773 0- Journal of Superconductivity and Novel Magnetism Springer US; http://www.springer-ny.com 24/1-2(2011-01-01), 717-720 1557-1939 24:1-2<717 2011 24 10948 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer