EPR investigation of superparamagnetism in nanometric-size LaFeO3±δ and La2NiO4±δ perovskites

Oliva, Cesare; Forni, L.

doi:10.1007/bf03162335

Cited by 9 publications

(1 citation statement)

References 13 publications

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“…Similar cases were reported for superparamagnetic particles with diameters ranging between 16 and 23 nm, i.e., larger than those here examined [81]. A model was proposed assuming that at enough high temperature the anisotropy energy of the samples was much smaller than k B T, (k B is the Boltzmann constant) namely of the thermal energy.…”

Section: Emrsupporting

confidence: 87%

Local Structure and Magnetism of Fe2O3 Maghemite Nanocrystals: The Role of Crystal Dimension

et al. 2020

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Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe2O3 maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma synthesis and commercial samples. Crystallite size was derived by electron microscopy and synchrotron powder diffraction, which was used also to investigate the crystallographic structure. The local atomic structure was inquired combining pair distribution function (PDF) and X-ray absorption spectroscopy (XAS). PDF revealed that reducing the crystal dimension induces the depletion of the amount of Fe tetrahedral sites. XAS confirmed significant bond distance expansion and a loose Fe-Fe connectivity between octahedral and tetrahedral sites. Molecular dynamics revealed important surface effects, whose implementation in PDF reproduces the first shells of experimental curves. The structural disorder affects the magnetic properties more and more with decreasing the nanoparticle size. In particular, the saturation magnetization reduces, revealing a spin canting effect. Moreover, a large effective magnetic anisotropy is measured at low temperature together with an exchange bias effect, a behavior that we related to the existence of a highly disordered glassy magnetic phase.

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Section: Emrsupporting

confidence: 87%