Тип публикации: статья из журнала
Год издания: 2024
Идентификатор DOI: 10.1134/S0031918X23603025
Ключевые слова: superparamagnetism, relaxation, ferrihydrite
Аннотация: The paper examines the impact of interparticle interactions on the superparamagnetic relaxation of ultrasmall nanoparticle ensembles, using Fe2O3∙<i>n</i>H2O iron oxyhydroxide (ferrihydrite) nanoparticles as an example. Two samples were analyzed: ferrihydrite of biogenic origin (with an average particle size of $\left\langle d \right\rangle $ ≈ 2.7 nm) with a natural organic shell, and a sample (with $\left\langle d \right\rangle $ ≈ 3.5 nm) that underwent low-temperature annealing, during which the organic shell was partially removed. The <i>DC</i> and <i>AC</i> magnetic susceptibilities (χ′(<i>T</i>), χ′′(<i>T</i>)) in a small magnetic field in the superparamagnetic (SPM) blocking region of the nanoparticles were measured. The results show that an increase in interparticle interactions leads to an increase in the SPM blocking temperature from 28 to 52 K according to DC magnetization data. It is shown that below the SPM blocking temperature, magnetic interactions of nanoparticles lead to the formation of a collective state similar to spin glass in bulk materials. The scaling approach reveals that the dynamics of correlated magnetic moments on the particle surface slow down with increasing interparticle interactions. Simulation of χ′′(<i>T</i>) dependence has shown that the dissipation of magnetic energy occurs in two stages. The first stage is directly related to the blocking of the magnetic moment of nanoparticles, while the second stage reflects the spin-glass behavior of surface spins and strongly depends on the strength of interparticle interactions.
Журнал: Physics of Metals and Metallography
Выпуск журнала: Т. 125, № 4
Номера страниц: 377-385
ISSN журнала: 0031918X
Место издания: Moscow
Издатель: Pleiades Publishing, Ltd.