Observation of enhanced dielectric coupling and room-temperature ferromagnetism in chemically synthesized BiFeO 3@SiO 2 core-shell particles

Mandar M. Shirolkar, Raja Das, Tuhin Maity, Pankaj Poddar, Sulabha K. Kulkarni

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

We report the effect of SiO 2 coating on the structural, magnetic, and dielectric properties of chemically synthesized high-purity BiFeO 3 particles. The as-synthesized BiFeO 3 particles demonstrate properties comparable with those reported for bulk BiFeO 3. On the other hand, the structural measurement on BiFeO 3@SiO 2 shows that the SiO 2 coating has anisotropically compressed the lattice of BiFeO 3 particles and stimulates the variation in the electron density. This affects magnetic and dielectric behavior of material. Frequency-dependent dielectric constant study at low temperature (20-325 K) revealed slight reduction (8-10%) in the dielectric constant of BiFeO 3@SiO 2 particles compared to uncoated BiFeO 3 particles. The study reveals five anomalies at 234, 206, 146, 84, and 25 K located in close proximity to the linear magnetodielectric coupling and spin reorientation transitions. The loss tangent (≈10 -3) and alternating current (ac) conductivity (≈10 -8 Ω -1cm -1) of BiFeO 3@SiO 2 particles are orders of magnitude lower than those observed for the BiFeO 3 particles. The magnetic measurement shows the existence of room-temperature ferromagnetism in BiFeO 3@SiO 2 particles with average value of magnetic moment per Fe atom ≈0.030 μ B and appreciable coercivity as high as 120 Oe. The canted spin structure in the surface shell of BiFeO 3@SiO 2 particles show an enhanced magnetic property and shifted hysteresis loop. The magnetic measurement in close proximity to dielectric transitions revealed enhanced magnetization, suggesting the presence of anisotropies. It has been observed that SiO 2 coating alters the properties of BiFeO 3 particles. Our dielectric and magnetic measurements show enhanced coupling among the electric and magnetic ordered parameters in BiFeO 3@SiO 2 core-shell particles compared to uncoated BiFeO 3 particles. The magnetic and dielectric properties of SiO 2-coated BiFeO 3 are similar to nanoparticles of BiFeO 3 where interface plays a significant role.

Original languageEnglish
Pages (from-to)19503-19511
Number of pages9
JournalJournal of Physical Chemistry C
Volume116
Issue number36
DOIs
Publication statusPublished - 13 Sep 2012
Externally publishedYes

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