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A series of Aurivillius-phase Bi 5 Ti 3 XO 15 (X = Cu, Mn, Ni, V) (BTXO: BTCuO, BTMnO, BTNiO and BTVO) were successfully prepared using a modified micro-pulling down method and their electric and magnetic properties were carefully studied. BTVO is ferroelectric at room temperature with a diamagnetic behavior due to the absence of magnetic ions in the compound. BTCuO and BTNiO show apparent ferroelectric behavior at room temperature (RT), contrarily to BTMnO which shows negligible polarization. In terms of their magnetic properties, BTMnO is a weak ferromagnetic (canted antiferromagnetic) at temperatures below 19 K, while BTCuO and BTNiO are basically paramagnetic at low temperature and possible with a short-range magnetic ordering at RT. We do not have any evidence showing the coexistence of both ferroelectric polarization and long range magnetic ordering in any of these compounds.

A series of Aurivillius-phase Bi 5 Ti 3 XO 15 (X = Cu, Mn, Ni, V) (BTXO: BTCuO, BTMnO, BTNiO and BTVO) were successfully prepared using a modified micro-pulling down method and their electric and magnetic properties were carefully studied. BTVO is ferroelectric at room temperature with a diamagnetic behavior due to the absence of magnetic ions in the compound. BTCuO and BTNiO show apparent ferroelectric behavior at room temperature (RT), contrarily to BTMnO which shows negligible polarization. In terms of their magnetic properties, BTMnO is a weak ferromagnetic (canted antiferromagnetic) at temperatures below 19 K, while BTCuO and BTNiO are basically paramagnetic at low temperature and possible with a short-range magnetic ordering at RT. We do not have any evidence showing the coexistence of both ferroelectric polarization and long range magnetic ordering in any of these compounds.

Novel multiferroic materials have attracted increasing attention in recent years. Aurivillius bismuth-layer structured Bi4Ti3O12·nBiFeO3 (BTFO: n = 1-3, 5) compounds with potential multiferroic properties are such a compound. However, the data on these BTFOs are ambigious, inconsistent, and incomplete. Therefore BTFOs were grown into single crystals for a systematic evaluation. Their crystal structures and microstructures show that intergrowth of layer structure occurs easily in this class of material. Their ferroelectric measurements show strong anisotropy and dielectric peaks at high temperature, accompanied by an abnormal loss that corresponds to their polar phase transition. At room temperature, ferroelectric hysteresis loops were successfully measured; the loops show a strong dependence in their polarization and coercive field on different values of n and anisotropy. Magnetic measurement shows that all the single crystals display magnetic transitions at high temperatures and weak ferromagnetism at room temperature. Electron spin resonance (ESR) results show the coexistence of ferromagnetic and paramagnetic signal components in all the compounds. Scanning probe microscope measurements show magnetic domains switched together with electric domains by use of an electric field. Therefore we conclude that overall spin disorder with localized order is the character of this class of material, with observed magnetoelectric (ME) coupling. This work could also point the way to novel multiferroic materials in locally magnetic ordered systems.

Novel multiferroic materials have attracted increasing attention in recent years. Aurivillius bismuth-layer structured Bi4Ti3O12·nBiFeO3 (BTFO: n = 1-3, 5) compounds with potential multiferroic properties are such a compound. However, the data on these BTFOs are ambigious, inconsistent, and incomplete. Therefore BTFOs were grown into single crystals for a systematic evaluation. Their crystal structures and microstructures show that intergrowth of layer structure occurs easily in this class of material. Their ferroelectric measurements show strong anisotropy and dielectric peaks at high temperature, accompanied by an abnormal loss that corresponds to their polar phase transition. At room temperature, ferroelectric hysteresis loops were successfully measured; the loops show a strong dependence in their polarization and coercive field on different values of n and anisotropy. Magnetic measurement shows that all the single crystals display magnetic transitions at high temperatures and weak ferromagnetism at room temperature. Electron spin resonance (ESR) results show the coexistence of ferromagnetic and paramagnetic signal components in all the compounds. Scanning probe microscope measurements show magnetic domains switched together with electric domains by use of an electric field. Therefore we conclude that overall spin disorder with localized order is the character of this class of material, with observed magnetoelectric (ME) coupling. This work could also point the way to novel multiferroic materials in locally magnetic ordered systems.

Novel multiferroic materials have attracted increasing attention in recent years. Aurivillius bismuth-layer structured Bi4Ti3O12·nBiFeO3 (BTFO: n = 1-3, 5) compounds with potential multiferroic properties are such a compound. However, the data on these BTFOs are ambigious, inconsistent, and incomplete. Therefore BTFOs were grown into single crystals for a systematic evaluation. Their crystal structures and microstructures show that intergrowth of layer structure occurs easily in this class of material. Their ferroelectric measurements show strong anisotropy and dielectric peaks at high temperature, accompanied by an abnormal loss that corresponds to their polar phase transition. At room temperature, ferroelectric hysteresis loops were successfully measured; the loops show a strong dependence in their polarization and coercive field on different values of n and anisotropy. Magnetic measurement shows that all the single crystals display magnetic transitions at high temperatures and weak ferromagnetism at room temperature. Electron spin resonance (ESR) results show the coexistence of ferromagnetic and paramagnetic signal components in all the compounds. Scanning probe microscope measurements show magnetic domains switched together with electric domains by use of an electric field. Therefore we conclude that overall spin disorder with localized order is the character of this class of material, with observed magnetoelectric (ME) coupling. This work could also point the way to novel multiferroic materials in locally magnetic ordered systems.

Novel multiferroic materials have attracted increasing attention in recent years. Aurivillius bismuth-layer structured Bi4Ti3O12·nBiFeO3 (BTFO: n = 1-3, 5) compounds with potential multiferroic properties are such a compound. However, the data on these BTFOs are ambigious, inconsistent, and incomplete. Therefore BTFOs were grown into single crystals for a systematic evaluation. Their crystal structures and microstructures show that intergrowth of layer structure occurs easily in this class of material. Their ferroelectric measurements show strong anisotropy and dielectric peaks at high temperature, accompanied by an abnormal loss that corresponds to their polar phase transition. At room temperature, ferroelectric hysteresis loops were successfully measured; the loops show a strong dependence in their polarization and coercive field on different values of n and anisotropy. Magnetic measurement shows that all the single crystals display magnetic transitions at high temperatures and weak ferromagnetism at room temperature. Electron spin resonance (ESR) results show the coexistence of ferromagnetic and paramagnetic signal components in all the compounds. Scanning probe microscope measurements show magnetic domains switched together with electric domains by use of an electric field. Therefore we conclude that overall spin disorder with localized order is the character of this class of material, with observed magnetoelectric (ME) coupling. This work could also point the way to novel multiferroic materials in locally magnetic ordered systems.

La0.1Bi0.9FeO3 (BFO), Bi0.5(Na0.85K0.15)0.5TiO3(BNKT) and BFO/BNKT nano-composite films were fabricated by pulsed laser deposition (PLD) method on Pt/Ti/SiO2/Si substrate. The ferroelectric properties were enhanced in BFO/BNKT compared to single layer film of BFO and BNKT. The ferroelectric domain structures were observed using piezoresponse force microscopy (PFM). The polarization reversal was time-dependent because the inhomogeneous domains with different coercivity. Evidence can also be seen in the fatigue results which showed unusual profile. The polarization increased as the increase of switching cycles because some of domains are difficult to switch using the applied field. Nano-scale piezoresponse hysteresis loops measured by PFM also revealed the local domain switching behavior in the BFO/BNKT film.

La0.1Bi0.9FeO3 (BFO), Bi0.5(Na0.85K0.15)0.5TiO3(BNKT) and BFO/BNKT nano-composite films were fabricated by pulsed laser deposition (PLD) method on Pt/Ti/SiO2/Si substrate. The ferroelectric properties were enhanced in BFO/BNKT compared to single layer film of BFO and BNKT. The ferroelectric domain structures were observed using piezoresponse force microscopy (PFM). The polarization reversal was time-dependent because the inhomogeneous domains with different coercivity. Evidence can also be seen in the fatigue results which showed unusual profile. The polarization increased as the increase of switching cycles because some of domains are difficult to switch using the applied field. Nano-scale piezoresponse hysteresis loops measured by PFM also revealed the local domain switching behavior in the BFO/BNKT film.

Ferroelectric/Piezoelectric K0.5Bi4.5Ti4O15 (KBT) film was fabricated by pulsed laser deposition method and confirmed by ferroelectric, dielectric measurements and local butterfly-type piezoresponse hysteresis loops. Importantly, ferroelectric domain switching by both electrical field and mechanical force in KBT film was demonstrated. The dark and bright contrast represents the PFM response of the up and down polarized domains, which can be written by a dc bias of ±12 V or a mechanical force of 40-50 nN. The successful demonstration of mechanical force switching of ferroelectric domain in KBT film other than electric field provides a novel mean for information storage and sensors.

La0.1Bi0.9FeO3 (BFO), Bi0.5(Na0.85K0.15)0.5TiO3(BNKT) and BFO/BNKT nano-composite films were fabricated by pulsed laser deposition (PLD) method on Pt/Ti/SiO2/Si substrate. The ferroelectric properties were enhanced in BFO/BNKT compared to single layer film of BFO and BNKT. The ferroelectric domain structures were observed using piezoresponse force microscopy (PFM). The polarization reversal was time-dependent because the inhomogeneous domains with different coercivity. Evidence can also be seen in the fatigue results which showed unusual profile. The polarization increased as the increase of switching cycles because some of domains are difficult to switch using the applied field. Nano-scale piezoresponse hysteresis loops measured by PFM also revealed the local domain switching behavior in the BFO/BNKT film.

La0.1Bi0.9FeO3 (BFO), Bi0.5(Na0.85K0.15)0.5TiO3(BNKT) and BFO/BNKT nano-composite films were fabricated by pulsed laser deposition (PLD) method on Pt/Ti/SiO2/Si substrate. The ferroelectric properties were enhanced in BFO/BNKT compared to single layer film of BFO and BNKT. The ferroelectric domain structures were observed using piezoresponse force microscopy (PFM). The polarization reversal was time-dependent because the inhomogeneous domains with different coercivity. Evidence can also be seen in the fatigue results which showed unusual profile. The polarization increased as the increase of switching cycles because some of domains are difficult to switch using the applied field. Nano-scale piezoresponse hysteresis loops measured by PFM also revealed the local domain switching behavior in the BFO/BNKT film.

Ferroelectric/Piezoelectric K0.5Bi4.5Ti4O15 (KBT) film was fabricated by pulsed laser deposition method and confirmed by ferroelectric, dielectric measurements and local butterfly-type piezoresponse hysteresis loops. Importantly, ferroelectric domain switching by both electrical field and mechanical force in KBT film was demonstrated. The dark and bright contrast represents the PFM response of the up and down polarized domains, which can be written by a dc bias of ±12 V or a mechanical force of 40-50 nN. The successful demonstration of mechanical force switching of ferroelectric domain in KBT film other than electric field provides a novel mean for information storage and sensors.