Room temperature ferroelectric and magnetic investigations and detailed phase analysis of Aurivillius phase Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} thin films

Journal Article · Sat Sep 01 00:00:00 EDT 2012 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4745936· OSTI ID:22089420

Keeney, Lynette; Kulkarni, Santosh; Deepak, Nitin; Schmidt, Michael; Petkov, Nikolay; Zhang, Panfeng F.; Roy, Saibal; Pemble, Martyn E.; Whatmore, Roger W. ^[1]; Cavill, Stuart ^[2]

---

1. Tyndall National Institute, University College Cork, 'Lee Maltings', Dyke Parade, Cork (Ireland)
2. Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

Aurivillius phase Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} (BTF7C3O) thin films on {alpha}-quartz substrates were fabricated by a chemical solution deposition method and the room temperature ferroelectric and magnetic properties of this candidate multiferroic were compared with those of thin films of Mn{sup 3+} substituted, Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Mn{sub 0.3}O{sub 15} (BTF7M3O). Vertical and lateral piezoresponse force microscopy (PFM) measurements of the films conclusively demonstrate that BTF7C3O and BTF7M3O thin films are piezoelectric and ferroelectric at room temperature, with the major polarization vector in the lateral plane of the films. No net magnetization was observed for the in-plane superconducting quantum interference device (SQUID) magnetometry measurements of BTF7M3O thin films. In contrast, SQUID measurements of the BTF7C3O films clearly demonstrated ferromagnetic behavior, with a remanent magnetization, B{sub r}, of 6.37 emu/cm{sup 3} (or 804 memu/g), remanent moment = 4.99 Multiplication-Sign 10{sup -5} emu. The BTF7C3O films were scrutinized by x-ray diffraction, high resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis mapping to assess the prospect of the observed multiferroic properties being intrinsic to the main phase. The results of extensive micro-structural phase analysis demonstrated that the BTF7C3O films comprised of a 3.95% Fe/Co-rich spinel phase, likely CoFe{sub 2-x}Ti{sub x}O{sub 4}, which would account for the observed magnetic moment in the films. Additionally, x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) imaging confirmed that the majority of magnetic response arises from the Fe sites of Fe/Co-rich spinel phase inclusions. While the magnetic contribution from the main phase could not be determined by the XMCD-PEEM images, these data however imply that the Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} thin films are likely not single phase multiferroics at room temperature. The PFM results presented demonstrate that the naturally 2D nanostructured Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} phase is a novel ferroelectric and has potential commercial applications in high temperature piezoelectric and ferroelectric memory technologies. The implications for the conclusive demonstration of ferroelectric and ferromagnetic properties in single-phase materials of this type are discussed.

• OSTI ID: 22089420
• Journal Information: Journal of Applied Physics, Vol. 112, Issue 5; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOMIC FORCE MICROSCOPY
BARIUM COMPOUNDS
EMISSION SPECTROSCOPY
FERROELECTRIC MATERIALS
FERROMAGNETIC MATERIALS
IRON COMPOUNDS
MAGNETIC CIRCULAR DICHROISM
MAGNETIC PROPERTIES
MAGNETIZATION
MAGNETOMETERS
MANGANESE COMPOUNDS
OXYGEN COMPOUNDS
PHOTOEMISSION
PIEZOELECTRICITY
SUBSTRATES
THIN FILMS
TITANIUM COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY