Subject Number : S-15-MS-1009
Support Type : Common use (including technical support necessary for the training)
Proposal Title (English) : Magnetic property of metal doped BiFeO3
Username (English) :　Bashir Ahmmad Arima
Affiliation (English) : Yamagata University

1. Summary
We have investigated the effects of temperature on the magnetic properties of the Bi0.9Gd0.1Fe1−xTixO3 (x = 0.00–0.20) multiferroic system. Unexpectedly, the coercive fields (Hc) of this multiferroic system increased with increasing temperature. The coercive fields and remanent magnetization were higher over a wide range of temperatures in sample x = 0.10. Therefore, we carried out temperature-dependent magnetization experiments extensively for sample x = 0.10. The exchange bias field (HEB) values increased with cooling magnetic fields (Hcool) and decreased with temperature. The HEB values were tunable by field cooling at temperatures of up to 250 K.

2. Experimental
Magnetization measurements of magnetic Bi0.9Gd0.1Fe1−xTixO3 nanoparticles and its parent ceramic samples were carried out using a SQUID, (Quantum Design MPMS-XL7, USA) both at zero field cooled (ZFC) and field cooled (FC) processes..)

3. Results and Discussion
The M-H hysteresis loops of nanoparticles were measured at different temperatures ranging from 20 K to 300 K with an applied magnetic field of up to ± 50 kOe. The Hc and Mr were extracted from the hysteresis loops and shown in Fig. 1. Both the Hc and Mr are higher for sample x = 0.10 than those for x = 0.00 and x = 0.20. The remarkable feature observed from Fig. 1 is that the coercivity of these ceramic samples increases with temperature. The temperature dependence magnetization measurements demonstrate clearly that both zero field cooled (ZFC) and field cooled (FC) curves of Bi0.9Gd0.1Fe0.9Ti0.1O3 ceramic coincide with each other. The influence of cooling magnetic fields on exchange bias effect at temperatures 150 K and 250 K in Bi0.9Gd0.1Fe0.9Ti0.1O3 multiferroic material (data not shown) shows that the exchange bias fields (HEB) increased significantly upon the application of cooling magnetic fields. This magnetically tunable exchange bias obtained in these samples up to temperatures 250 K is promising for application, as most of the materials show exchange bias only far below room temperature.

Fig 1: Variation of Hc (a) and Mr (b) as a function of temperatures.　
4. Acknowledgements
KAKENHI (No. 26810117) and Nanotechnology Platform Program (Molecule and Material Synthesis) of MEXT, Japan.
5. Publication/Presentation
(1) B. Ahmmad, M.Z. Islam, A. Billah, M.A. Basith, J. Phys. D: Appl. Phys. Vol. 49 (2016) pp.095001.
(2) M. A. Basith, F. A. Khan, B. Ahmmad, S. Kubota, et. al., J. Appl. Phys. Vol. 118 (2015) pp.023901