Abstract
Ferromagnetic resonance was used to study the temperature dependence of mixed manganesecobalt ferrite nanoparticles. The hydrothermal method was used to synthesize the Mn x Co 1−x Fe 2 O 4 nanoparticles. The structural characterization was carried out using X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM), obtaining a nanoparticles size range between 5-60 nm. Magnetization curves M(H) as a function of the Mn 2+ content at 2.5 and 300 K, and ferromagnetic resonance (FMR) in the temperature range of 80 < T < 700 K were used for the magnetic characterization. The FMR spectra show asymmetric signals characteristic of the strong magnetic anisotropies. The temperature dependence of the resonance field shows three differentiated regions, a low-temperature region in which the resonance is attributed to agglomerates of nanoparticles, an intermediate temperature region where the resonance is characteristic of dispersed magnetic nanoparticles, and a third region over the blocking temperature corresponding to a superparamagnetic behavior of the system. The study of the H R and the peak to peak linewidth as a function of the temperature and Mn 2+ content allows us to accurately elucidate the key characteristics of the deviation from the ideal superparamagnetic behavior observed by magnetic measurements and open up new research possibilities for evaluating interparticle interactions in nanoparticles.