Multiferroics
Recently, there has been a great interest for the study of the multiferroic materials, in which ferromagnetic, ferroelectric, and/or ferroelastic orderings coexist. The co-existence of \quotes{ferro}-orders in multiferroics opens up pathways for the possibility that the magnetization can be controlled by the electric field and vice versa. The ability to manipulate the magnetic and ferroelectric properties of multiferroic BiFeO3 (BFO) by dopants opens up promising opportunities for fabricating new multiferroic materials in the field of information storage technology. Noticeably, the spiral modulated spin structure (SMSS) of BFO possesses an incommensurate long-wavelength period of 62 nm due to which the macroscopic magnetization gets cancelled. As a result, the linear magnetoelectric effect is no longer observed. Moreover, the preparation of undoped BFO is challenging due to the formation of different impurity phases. Thus the use of undoped bulk BFO in functional applications gets rather limited due to these hindrances. To improve the multiferroic properties of BFO, one of the easiest ways is to perturb the SMSS by substituting Bi and Fe in BFO by some cations. Therefore, the aim of this research project is minor substitution of Bi and Fe in BiFeO3 by rare earth and transitional metal ions, respectively to enhance its multiferroicity.
In a recent work, undoped BiFeO3 , Gd doped Bi0.9Gd0.1FeO3, and Gd-Ti co-doped Bi0.9Gd0.1Fe1-xTixO3 (x = 0.10, 0.20) materials were synthesized in our laboratory to report their multiferroic properties. The structural analysis and phase identification of these multiferroic ceramics were performed using Rietveld refinement. This analysis has confirmed the high phase purity of the 10% Gd-Ti co-doped Bi0.9Gd0.1Fe1-xTixO3 sample compared to that of other compositions under investigation. The major phase of this particular composition is of rhombohedral R3c type structure (wt% > 99%) with negligible amount of impurity phases. In terms of characterization, we address magnetic properties of this co-doped ceramic system by applying substantially a higher magnetic field. Additionally, the leakage current density has been measured to explore its effect on the ferroelectric properties of this multiferroic system. The outcome of this investigation suggests that the substitution of 10% Gd and Ti in place of Bi and Fe, respectively, in BiFeO3 significantly enhances its multiferroic properties. The improved multiferroic properties obtained by 10\% Gd and Ti co-doping in BiFeO3 is promising for novel multifunctional device applications. Our investigations further conclude that an appropriate choice of co-doping elements and fine composition adjustment are keys to optimize the multiferroic properties of BiFeO3 ceramics.
Selected publications based on this research project:
1.The 10% Gd and Ti co-doped BiFeO3: A promising multiferroic material.
M. A. Basith, Areef Billah, M. A. Jalil, Nilufar Yesmin, Mashnoon Alam Sakib, Emran Khan Ashik, S. M. Enamul Hoque Yousuf, Sayeed Shafayet Chowdhury, Md. Sarowar Hossain, Shakhawat H. Firoz and Bashir Ahmmad, Journal of Alloys and Compounds (Publisher: Elsevier), 694, 792-799, 2016.
2.Anomalous coercivity enhancement with temperature and tunable exchange bias in Gd and Ti co-doped BiFeO3 multiferroics.
Bashir Ahammad, M. Z. Islam, Areef Billah and M. A. Basith, Journal of Physics D: Applied Physics (Publisher: IOP Science, UK), 49, 095001, 2016.
3.Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO3 ceramics.
M. A. Basith, O. Kurni, M. S. Alam, B. L. Sinha and Bashir Ahammad, Journal of Applied Physics (Publisher:American Institute of Physics), vol. 115, 024102, 2014.