Scanning probe imaging of coexistent ferromagnetism and ferroelectricity at room temperature

Abstract

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...

Investigations on Fe doped Ba0.95Sr0.05TiO3 single phase magnetodielectric compounds

“…In the third approach the magnetic ions like Fe, Co, Ni, W, Mn etc. are substituted in ABO 3 type ferroelectric systems [12][13][14][15][16][17][18]. The literature referred between 1 and 14 above are a few examples of each category and not a comprehensive review.…”

“…In past a few years, Fe doped PbTiO 3 has been investigated for its multiferroic properties [12][13][14]. It is observed that the PbTiO 3 matrix shows a solid solubility for concentration of Fe as large as 50 mol% and the compound PbFe 0.5 Ti 0.5 O 3 show a co-existence of ferroelectric and magnetic orders at room temperature, even in the thin film form [12].…”

Investigations on Fe-doped strontium barium niobate, single phase ferroelectric and magnetodielectric compounds

“…It is already reported that the Fe-doped PbTiO 3 and Pb(Sr)TiO 3 show the presence of the ferroelectric and ferromagnetic orders at room temperature. 15,16 Taking into consideration the observations above, it is proposed to investigate Fe-doped SBN systems, such that the ferroelectric transition temperature of the resulting systems occur in the vicinity of room temperature. A possible virtue of these compositions would be a remarkable magnetodielectric coupling, measured in terms of the magneto-capacitance (M c Þ, defined as M c ¼ ½"ðHÞ À "ð0Þ="ð0Þ, where "ðHÞ and "ð0Þ are the dielectric constants in the presence and absence of the applied magnetic field.…”

Observation of thickness dependent properties in novel multiferroic thin films

“…Moreover, most of the known multiferroic systems are typically antiferromagnetic with transition temperatures below room temperature [1,2]. Recently we have been successful in achieving room temperature multiferroicity in bulk as well as thin films of PbTi 1-x Fe x O 3 system [3,4]. We have also demonstrated the existence of similar properties in bulk and thin films of Bi 0.9-x M x La 0.1 FeO 3 ( M -Tb, Dy) [5][6][7].…”