Nuclear Magnetic Resonance in Hexaferrite/Maghemite Composite Nanoparticles
P. Křišťana, O. Hondlík b, H. Štěpánková a, V. Chlan a, K. Kouřil a, R. Řezníček a, E. Pollert c and P. Veverka c
aCharles University in Prague, Faculty of Mathematics and Physics, V Holešovičkách 2, 18000 Prague 8, Czech Republic
bFaculty of Biomedical Engineering, Czech Technical University in Prague, Sítná sq. 3105, 27201 Kladno, Czech Republic
cInstitute of Physics, ASCR, Cukrovarnická 10, 16253 Prague 6, Czech Republic
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Due to their bio-compatibility and non-toxicity, ferrimagnetic iron oxides are suitable for various medical applications. In the case of hyperthermia, the promising approach how to reach desired magnetic properties is to combine more phases into a composite material. A series of samples containing maghemite and M-hexaferrite was prepared by sol-gel method with subsequent thermal treatment where annealing temperature and time were varied. The samples were characterized by X-ray diffraction. In this paper we focused mainly on application of nuclear magnetic resonance spectroscopy to investigate these strongly inhomogeneous nanoparticle composites. Frequency-swept 57Fe NMR spectra of nanoparticle samples were measured in a zero external magnetic field at 4.2 K. Utilizing differences in optimal excitation field strengths and in relaxation times, we were able to resolve NMR signal assigned to hexagonal ferrite of M-phase from signal which showed features attributed to maghemite.

DOI: 10.12693/APhysPolA.127.514
PACS numbers: 76.60.-k, 75.50.Gg, 75.50.Tt, 75.47.Lx, 61.66.Fn