Temperature dependence of the ferromagnetic resonance (FMR) for MnxCo1−xFe2O4 (0 ≤ x ≤ 1) nanoparticles

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.

Observation of intrinsic fluorescence in cobalt ferrite magnetic nanoparticles by Mn2+substitution and tuning the spin dynamics by cation distribution

“…18; however, the resonance field shifted towards the higher magnetic field of 3497.6 G with DH pp of 925.9 G. This can be attributed to the increase in particle size, which resulted in an interaction between the individual domains separated by a domain wall. 20,98 A further increase in the Mn 2+ concentration led to an increase in the broadness of the FMR spectrum; however, the resonance field decreased for the Co 1Àx Mn x Fe 2 O 4 (x = 0.4 and 0.6) samples and increased for the Co 1Àx Mn x Fe 2 O 4 (x = 0.8) sample concentration. The change in the resonance field and peak-to-peak width of the Mn 2+ -substituted NFs can also be correlated with the cation distribution and change in the crystallite size.…”