Large structure-dependent room temperature exchange bias in self-assembled BiFeO3 nanoparticles
| Autor: | Goswami, Sudipta, Sahoo, Aditi, Bhattacharya, Dipten, Karci, Ozgur, Mohanty, P. K. |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | APL Mater. 8, 081101 (2020) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1063/5.0015339 |
| Popis: | We studied the magnetic properties of self-assembled aggregates of BiFeO3 nanoparticles (~ 20-40 nm). The aggregates formed two different structures - one with limited and another with massive cross-linking - via `drying-mediated self-assembly' process following dispersion of the nanoparticles within different organic solvents. They exhibit large coercivity H_C (>1000 Oe) and exchange bias field H_E (~ 350-900 Oe) in comparison to what is observed in isolated nanoparticles (H_C ~ 250 Oe; H_E ~ 0). The H_E turns out to be switching from negative to positive depending on the structure of the aggregates with |H_E| being larger. The magnetic force microscopy reveals the magnetic domains (extending across 7-10 nanoparticles) as well as the domain switching characteristics and corroborate the results of magnetic measurements. Numerical simulation of the `drying-mediated-self-assembly' process shows that the nanoparticle-solvent interaction plays an important role in forming the `nanoparticle aggregate structures' observed experimentally. Numerical simulation of the magnetic hysteresis loops, on the other hand, points out the importance of spin pinning at the surface of nanoparticles as a result of surface functionalization of the particles in different suspension media. Depending on the concentration of pinned spins at the surface pointing preferably along the easy-axis direction - from greater than 50\% to less than 50% - H_E switches from negative to positive. Quite aside from bulk sample and isolated nanoparticle, nanoparticle aggregates - resulting from surface functionalization - therefore, offer remarkable tunability of properties depending on structures. Comment: 14 pages, 33 pdf figures. Contact authors for the supplementary data and movies |
| Databáze: | arXiv |
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