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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:09 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Solid State Physics and Materials Science
Title:
Specific aspects of magnetic relaxation in nanoparticulate systems
Authors:
V. Kuncser
Affiliation:
National Institute of Materials Physics, 077125, Bucharest-Magurele, Romania
E-mail
kuncser@infim.ro
Keywords:
nanoparticulate systems, magnetic relaxation, characteristic time, measurement time window, bio-medical applications
Abstract:
Magnetic nanoparticles show presently a wide range of high technology applications in different fields, starting from engineering to bio-medicine. Their associated variety of magnetic behaviors is related to the interplay between the intrinsic material properties, finite size effects and interphase/interparticle interactions. Finite size effects and inter-particle interactions have a strong effect on the magnetic relaxation phenomena, which directly influence the magnetic response of the system to be used in a specific application. Therefore many efforts have been done in the last period to fully understand and characterize different nanoparticulate systems in regard to magnetic relaxation phenomena. Specific characterization methodologies based on temperature and field dependent Mossbauer spectroscopy and SQUID magnetometry are briefly discussed. Zero field cooling-field cooling procedures as well as various temporal dependences of magnetization, strictly dependent on the initial setting of the spin system, are theoretically introduced and subsequently discussed with respect to experimental results. A special attention is focused on the procedure of deriving the blocking temperature (seen as the temperature defining the transition to the superparamagnetic state) by dynamic methods of different time windows. It is shown that the material dependent characteristic time τ0 in a Neel type relaxation can be derived with accuracy only by combining dynamic methods of significantly different time windows, as for example a.c. susceptibility and Mossbauer spectroscopy. The importance of such efficient magnetic characterization related to bio-medical applications is also briefly discussed.
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