We report here synthesis of phase-pure magnetoelectric BiFeO3 thin films with controlled oxygen stoichiometry on Pt/TiO2/SiO2/Si substrate using pulsed-laser deposition technique. Saturated ferroelectric hysteresis loop has been observed in phase-pure and highly resistive BiFeO3 thin films. The dielectric response study of the films with temperature indicates an anomaly in dielectric constant ε(T), in the vicinity of Néel temperature (∼380 °C). This anomaly in ε(T) is explained as an influence of vanishing magnetic ordering on electric ordering of magnetoelectric BiFeO3 sample.

Room temperature coexistence of ferromagnetism and ferroelectricity in a thin film of a novel material of nominal composition PbTi 0.5 Fe 0.5 O 3 - is probed by standard ferroelectric and ferromagnetic hysteresis loop measurements and by scanning probe microscopy of various kinds.Both magnetic domains and ferroelectric domains are observed in the same spatial region of the material, implying phase coexistence in this system. For both order parameters, sample morphology strongly affects roughness of the domain walls. PACS: 75.80.+q, 85.40, 68.64.Dz ________________________________________________________________ Recent resurgence of interest in multiferroic systems in general, and in magnetoelectric systems in particular, is driven by two different reasons, namely, the basic physics of coexistence of two order parameters in the ground state and the possibility of using this coexistence, and a possible coupling between them, for devising novel applications [1][2]. Magnetoelectric systems, which exhibit coexistence of magnetism and ferroelectricity with a possible coupling between the two order parameters, are of particular importance, especially when the magnetism is of the ferromagnetic variety. Multifunctional and exotic non-volatile memory applications are possible in that case. However, the presence of local spins and of off-centered structural distortion are basic requirements for magnetic and ferroelectric properties, respectively and naturally, these two seemingly unrelated phenomena rarely co-exist at room temperature. Unfortunately, most of the known multiferroic systems are antiferromegnetic with transition temperatures below room temperature [3,4]. Therefore, for device applications these materials hardly find any use.Recently, we have reported novel materials exhibiting magnetoelectric properties at room temperature [5][6][7]. In this letter we report room temperature multiferroic properties for lower compared to any of these phases. It is essential to reproduce these properties in thin films for their usefulness in practical applications, as well as for further basic physics investigations. In this letter we report that thin films of this material, grown on Pt/TiO 2 /SiO 2 /Si substrate by using Pulsed Laser Deposition (PLD) technique, preserve the room temperature multiferroic nature of this system. More importantly we are successful in demonstrating the phase coexistence occurring at microscopic scale as well.In order to achieve good chemical homogeneity and controlled stoichiometry, Pb(Ti 0.5 Fe 0.5 )O 3- powder sample was prepared by using wet chemical route (co-precipitation).The detailed procedure for synthesis is described elsewhere [7]. From Nominal composition (with Fe +3 replacing Ti +4 ) one would expect the system to be an electrical conductor. Instead, we have been able to synthesize samples, which are insulating. Powder samples thus prepared were compacted and sintered at 1000 C/2hr. to obtain dense target for the laser ablation process.Sintering was carried out in PbO atmosph...

It has been demonstrated that Si substitution in a PbTiO3 target helps to avoid the formation of a pyrochlore phase, which otherwise occurs during fabrication of the films directly on Si(100) by the pulsed laser deposition technique. The films are perfectly c-axis oriented. Moreover, the ferroelectric properties of PbTiO3 are not affected by Si substitution. As silicon helps the realization of the films at low substrate temperature, the Pb/Ti ratio is maintained close to 1 and the loss factor tan δ in the range of 0.02–0.05. Thus, the integration of nonvolatile ferroelectric random access memory on semiconductors is shown to be possible in a reliable, cost effective, and simple manner.

No abstract

No abstract