Theoretical and experimental studies on the influence of Cr incorporation on the structural, optical, and magnetic properties of Bi0.5K0.5TiO3 materials

• Published in: Journal of sol-gel science and technology Vol. 87; no. 3; pp. 528 - 536
• Main Authors: Tuan, Nguyen Hoang, Anh, Vuong Kha, Doan, Nguyen Ba, Bac, Luong Huu, Dung, Dang Duc, Odkhuu, Dorj
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-09-2018; Springer Nature B.V
• Subjects: BriefCommunication: Sol–gel and hybrid materials for dielectric; Ceramics; Chemistry and Materials Science; Chromium; Composites; Density functional theory; electronic; Energy gap; ferroelectric applications; Ferroelectric materials; Ferroelectricity; Ferromagnetism; Glass; Inorganic Chemistry; Jahn-Teller effect; Lead free; magnetic; Magnetic properties; Magnetic saturation; Magnetism; Materials Science; Multiferroic materials; Nanocrystals; Nanotechnology; Natural Materials; Optical and Electronic Materials; Optical properties; Sol-gel processes; Titanium; Transition metals; Bi; Density functional theory; Ferromagnetism; K; TiO; Sol–gel; Multiferroic
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-018-4764-1

Multiferroic materials based on lead-free ferroelectric materials have potential applications in the fabrication of next-generation devices. Herein, the sol–gel method is used to synthesize pristine and Cr-doped Bi
0.5
K
0.5
TiO
3
nanocrystals. Density functional theory simulation is performed to elucidate the mechanism underlying the observed electronic and magnetic properties of the nanocrystals. In materials doped with 9 mol% Cr, the substitution of Cr in the Ti site decreases the optical band gap from 3.09 eV to 2.26 eV and induces ferromagnetism at room temperature. The saturation magnetization of the materials is approximately 0.18 
μ
B
/Cr at 5 K and can be attributed to the interplay of the unpaired electron counts of Cr
3+
ions in the crystal field mechanism and Jahn–Teller effect. Pristine Bi
0.5
K
0.5
TiO
3
samples exhibit weak ferromagnetism at room temperature, given the existence of the mixed valence states of Ti
4+
and Ti
3+
and the formation of O or Ti vacancies during sample growth. The present study provides deep insight into the induction of magnetism in ferroelectric materials doped with transition metals. Such materials have potential spintronic applications.
Highlights
The Cr-doped Bi
0.5
K
0.5
TiO
3
materials were fabricated by the sol–gel method.
The room-temperature ferromagnetism in Cr-doped samples was obtained.
Optical band gap was reduced from 3.09 eV to 2.26 eV.
Defect-induced room-temperature ferromagnetism was investigated by density functional theory calculations.