Qualitative Evaluation of the Magnetocrystalline Anisotropy in Spinel Ferrite Nanoparticles Using Polarized Neutron Powder Diffraction

nanoparticles with different Co contents (x = 0.11 and 0.61) using polarized neutron powder diffraction (PNPD). The off-diagonal elements of the susceptibility tensors and degree of asymmetry of the magnetization ellipsoids obtained from the PNPD refinements reveal that the sample with x = 0.61 presents a larger magnetocrystalline anisotropy than the sample with x = 0.11, which is consistent with the effective anisotropy derived from magnetometry. Moreover, comparison of the PNPD-derived magnetization ellipsoids across materials with varying anisotropies confirms the direct relationship between the ellipsoid asymmetry and magnetocrystalline anisotropy. These findings establish PNPD as a powerful tool for qualitatively probing intrinsic anisotropies in nanoparticle systems, paving the way for the rational design and optimization of magnetic nanoparticles for advanced applications.