Greatly Reduced Leakage Current in Ti- and La-doped Bi 2 FeCrO 6 Prepared by High Pressure Synthesis
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Greatly Reduced Leakage Current in Ti- and La-doped Bi2FeCrO6 Prepared by High Pressure Synthesis Feiming Bai1, Lihong Dai1, Lei Shi1 and Huaiwu Zhang1 1 State Key Laboratory of Electronic Thin films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China, 610054 ABSTRACT Undoped Bi2FeCrO6, 5%Ti- and 10%La-doped Bi2FeCrO6 were prepared by a high pressure solid-state sintering method. The phase structure, electrical, ferroelectric and magnetic properties have been investigated. It is shown that undoped Bi2FeCrO6 has a serious leakage current problem, and doping either Ti or La can enhance the resistivity by 2-3 orders of magnitude. Furthermore, both Ti- and La-doped Bi2FeCrO6 show an antiferromagnetic spin order due to disordered B-site cation alignment. Weak ferromagnetism was only observed in undoped Bi2FeCrO6 and the reason is tentatively explained. INTRODUCTION Single-phase multiferroic materials with more than one order parameters have attracted long-term interest because of their fundamental physics and potential use in technological applications [1-3]. However, room-temperature (RT) multiferroic is still scare due to the incompatible requirement for the coexistence of ferromagnetism and ferroelectricity [4]. Previously, Baettig et al. has proposed that double perovskite Bi2FeCrO6 (BFCO) have a superior saturated magnetization and comparable ferroelectric polarization to those values of well-known BiFeO3 [5]. Since ferromagnetic materials tend to be metallic and are not suitable to sustain polarization, insulating materials with either an antiferromagnetic or ferrimagnetic spin order are considered as good candidates for RT multiferroic. Motivated by this prediction, high saturated magnetization of 0.4 μB/f.u. (30 emu/cm3) has been first observed in (111)-oriented BFCO epitaxial thin films, indicating ferrimagnetic nature [6]. However, very contradictive results were then reported: a ferromagnetic spin order with magnetic moment of 1.7 μB/f.u. was reported in BiFeO3/BiCrO3 (111) superlattice grown on SrTiO3(111) substrate[7], and an antiferromagnetic one with magnetic moment as low as 0.02μB/f.u. was reported in BFCO film by sequentially depositing BiFeO3 and BiCrO3 on SrTiO3(100) substrate [8]. The latter is almost same with that of bulk BFCO, which was believed to have completely disordered cation alignment [9]. In all cases mentioned above, BFCO samples have been found to show a serious leakage current problem at room temperature, therefore, polarization can only be measured at low temperature [6-9]. In current work, bulk Bi2FeCrO6 samples are prepared by high pressure solid-sate sintering. It is shown that the resistivity of bulk sample can be greatly enhanced by substituting A-site Bi3+ by lanthanum (La) or B-site Fe3+ and Cr3+ by titanium (Ti).
EXPERIMENT Bi2FeCrO6, Bi1.8La0.2FeCrO6 (BLFCO) and Bi2(Fe0.9Cr0.9Ti0.1)O6 (BFCTO) ceramic samples were synthesized in a DS6×8MN cubic press [10]. The cell temperature was measured directly using a PtRh6%–PtRh30% thermocoup
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