2017/03/21 by Pavana S. V. Mocherla, M. B. Sahana, Mocherla, Pavana S. V. +19
Engineering · Materials Science · Physics and Astronomy · #Characterization and Applications of Magnetic Nanoparticles #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Multiferroics and related materials #Theoretical and Computational Physics #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.1703.07190
44 pages, 15 figures
arxiv created 2017/03/21 · openalex publication_date 2017/03/21 · arxiv updated 2017/03/22 · openalex created_date 2017/08/31 · openalex updated_date 2026/07/28
Magnetization of antiferromagnetic nanoparticles is known to generally scale up inversely to their diameter (d) according to Néel's model. Here we report a deviation from this conventional linear 1/d dependence, altered significantly by the microstrain, in Ca and Ti substituted BiFeO3 nanoparticles. Magnetic properties of microstrain-controlled Bi1-xCaxFe1-yTiyO3-delta (y = 0 and x = y) nanoparticles are analyzed as a function of their size ranging from 18 nm to 200 nm. A complex interdependence of doping concentration (x or y), annealing temperature (T), microstrain (epsilon) and particle size (d) is established. X-ray diffraction studies reveal a linear variation of microstrain with inverse particle size, 1/d nm-1 (i.e. epsilon.d = 16.5 nm.%). A rapid increase in the saturation magnetization below a critical size dc ~ 35 nm, exhibiting a (1/d)alpha (alpha ~ 2.6) dependence, is attributed to the influence of microstrain. We propose an empirical formula M is proportional to (1/d)epsilonbeta (beta ~ 1.6) to highlight the contributions from both the size and microstrain towards the total magnetization in the doped systems. The magnetization observed in nanoparticles is thus, a result of competing magnetic contribution from the terminated spin cycloid on the surface and counteracting microstrain present at a given size. Large magnetodielectric response of ~ 9.5 % is observed in spark plasma sintered pellets with optimal size and doping concentration, revealing a strong correlation between magnetic and ferroelectric order parameters.