Combined strain + doping method is used in a VAN system to realise exemplary properties which can... more Combined strain + doping method is used in a VAN system to realise exemplary properties which cannot be realised in plain films.
The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2... more The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2MnO3 (LCMO) thin films grown on two types of substrates, SrTiO3 (001) (STO) and LaAlO3 (001) (LAO) has been studied as a function of film thickness within the range of 25-300 nm. The STO substrate imposes an in-plane tensile biaxial strain while LAO substrate imposes an in-plane compressive biaxial strain. The in-plane biaxial strain on LCMO by STO substrate gets relaxed more rapidly than that by LAO substrate but both LCMO/STO and LCMO/LAO show a maximum entropy change (∆SM) of ∼ 12.
In this work, heteroepitaxial vertically aligned nanocomposite (VAN) La 0.9 Ba 0.1 MnO 3 (LBMO)-C... more In this work, heteroepitaxial vertically aligned nanocomposite (VAN) La 0.9 Ba 0.1 MnO 3 (LBMO)-CeO 2 films are engineered to produce ferromagnetic insulating (FMI) films. From combined X-ray photoelectron spectroscopy, X-ray diffraction, and electron microscopy, the elimination of the insulator−metal (I−M) transition is shown to result from the creation of very small lateral coherence lengths (with the corresponding lateral size ∼ 3 nm (∼7 u.c.)) in the LBMO matrix, achieved by engineering a high density of CeO 2 nanocolumns in the matrix. The small lateral coherence length leads to a shift in the valence band maximum and reduction of the double exchange (DE) coupling. There is no "dead layer" effect at the smallest achieved lateral coherence length of ∼3 nm. The FMI behavior obtained by lateral dimensional tuning is independent of substrate interactions, thus intrinsic to the film itself and hence not related to film thickness. The unique properties of VAN films give the possibility for multilayer spintronic devices that can be made without interface degradation effects between the layers.
Magnetoelectric systems could be used to develop magnetoelectric random access memory and microse... more Magnetoelectric systems could be used to develop magnetoelectric random access memory and microsensor devices. One promising system is the two-phase 3-1-type multiferroic nanocomposite in which a one-dimensional magnetic column is embedded in a three-dimensional ferroelectric matrix. However, it suffers from a number of limitations including unwanted leakage currents and the need for biasing with a magnetic field. Here we show that the addition of an antiferromagnet to a 3-1-type multiferroic nanocomposite can lead to a large, self-biased magnetoelectric effect at room temperature. Our three-phase system is composed of a ferroelectric Na0.5Bi0.5TiO3 matrix in which ferrimagnetic NiFe2O4 nanocolumns coated with antiferromagnetic p-type NiO are embedded. This system, which is self-assembled, exhibits a magnetoelectric coefficient of up to 1.38 × 10–9 s m–1, which is large enough to switch the magnetic anisotropy from the easy axis (Keff = 0.91 × 104 J m–3) to the easy plane (Keff = –1.65 × 104 J m–3). A three-phase system that is composed of a ferroelectric Na0.5Bi0.5TiO3 matrix in which ferrimagnetic NiFe2O4 nanocolumns coated with antiferromagnetic p-type NiO are embedded exhibits self-biased magnetoelectric switching at room temperature.
Goal To determine patient-reported financial and family burden associated with treatment of cance... more Goal To determine patient-reported financial and family burden associated with treatment of cancer in the previous 28 days across Canada. Methods A self-administered questionnaire (P-SAFE v7.2.4) was completed by 901 patients with cancer from twenty cancer centres nationally (344 breast, 183 colorectal, 158 lung, 216 prostate) measuring direct and indirect costs related to cancer treatment and foregone care. Monthly self-reported out-of-pocket-costs (OOPCs) included drugs, homecare, homemaking, complementary/ alternative medicines, vitamins/supplements, family care, accommodations, devices, and “other” costs. Travel and parking costs were captured separately. Patients indicated if OOPC, travel, parking, and lost income were a financial burden. Results Mean 28-day OOPCs were CA$518 (US Purchase Price Parity [PPP] $416), plus CA$179 (US PPP $144) for travel and CA$84 (US PPP $67) for parking. Patients self-reporting high financial burden had total OOPCs (33%), of CA$961 (US PPP $772),...
Orthorhombic RMnO3 (R = rare-earth cation) compounds are type-II multiferroics induced by inversi... more Orthorhombic RMnO3 (R = rare-earth cation) compounds are type-II multiferroics induced by inversion-symmetry-breaking of spin order. They hold promise for magneto-electric devices. However, no spontaneous room-temperature ferroic property has been observed to date in orthorhombic RMnO3. Here, using 3D straining in nanocomposite films of (SmMnO3)0.5((Bi,Sm)2O3)0.5, we demonstrate room temperature ferroelectricity and ferromagnetism with TC,FM ~ 90 K, matching exactly with theoretical predictions for the induced strain levels. Large in-plane compressive and out-of-plane tensile strains (−3.6% and +4.9%, respectively) were induced by the stiff (Bi,Sm)2O3 nanopillars embedded. The room temperature electric polarization is comparable to other spin-driven ferroelectric RMnO3 films. Also, while bulk SmMnO3 is antiferromagnetic, ferromagnetism was induced in the composite films. The Mn-O bond angles and lengths determined from density functional theory explain the origin of the ferroelectri...
Annually, thousands of individuals die and tens of thousands are hospitalized in association with... more Annually, thousands of individuals die and tens of thousands are hospitalized in association with suspected adverse drug reactions (ADRs) in Canada. We analyzed the reports from the Canada Vigilance Adverse Reaction online database and present a synopsis of the state of ADRs in Canada between 2009 and 2018. Our synopsis includes both cross-sectional and longitudinal insights into ADR demographics, outcomes, associated drugs and disease indications. In closing, we highlight five overarching issues uncovered in our analysis, which have potential implications for future policy formulation. Further in-depth exploration is required to shine some additional light on these issues.
Three-dimensional (3D) strain induced in self-assembled vertically aligned nanocomposite (VAN) ep... more Three-dimensional (3D) strain induced in self-assembled vertically aligned nanocomposite (VAN) epitaxial films provides an unrivaled method to induce very large strains in thin films. Here, by growing VAN films of EuTiO (ETO)-Eu O (EO) with different EO fractions, the vertical strain was systematically increased in ETO, up to 3.15%, and the Eu-Ti-Eu bond angle along <111> decreased by up to 1°, leading to a weakening of the antiferromagnetic interactions, and switching from antiferromagnetic to ferromagnetic behaviour. Our work has shown for the first time that Eu-Ti-Eu superexchange interactions play a key role in determining the magnetic ground state of ETO. More broadly, our work serves as an exemplar to show that multifunctionalities in strong spin-lattice coupling perovskite oxides can be uniquely tuned at the atomic scale using simple VAN structures.
The effect of interface roughness of ferromagnetic and antiferromagnetic layers on exchange bias ... more The effect of interface roughness of ferromagnetic and antiferromagnetic layers on exchange bias is still not well understood. In this report we have investigated the effect of surface roughness in (111)oriented antiferromagnetic CoO films on exchange bias with ferromagnetic Fe grown on top. The surface roughness is controlled at the atomic scale, over a range below ~ 0.35 nm, by varying layer thickness of the CoO films. It is observed that both exchange bias field (H E) and coercivity (H C) extensively depend on the atomic scale roughness of the CoO (111) at the interface with Fe film. An opposite dependence of H E and H C on interface roughness was found, which was ascribed to partially compensated spin states induced by the atomic roughness at the fully uncompensated CoO (111) surfaces and was corroborated using the Monte Carlo simulations. Moreover, the onset temperature for H C is found to be up to ~ 80 K below the blocking temperature (T B) and the temperature dependence-2-of H C follows the power law with a critical exponent equal to one, which indicates that, in this system, H C is more of an interface-related property than H E .
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
UCC Library and UCC researchers have made this item openly available. Please let us know how this... more UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Exploring ferroelectric and magnetic properties of Tb-substituted m = 5 layered Aurivillius phase thin films
UCC Library and UCC researchers have made this item openly available. Please let us know how this... more UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Magnetic properties of microwave-plasma (thermal) chemical vapour deposited Co-filled (Fe-filled) multiwall carbon nanotubes: comparative study for magnetic device applications
In this paper, the magnetic properties of Co-rich CoPtP films electrodeposited using an optimized... more In this paper, the magnetic properties of Co-rich CoPtP films electrodeposited using an optimized Pulse Reverse (PR) technique are investigated for magnetic MEMS applications. By using a combination of forward and reverse pulse with optimized duty cycles during deposition and suitable bath chemistry, the film stress is reduced significantly, which results in smooth, crack-free films of thickness up to 26 µm. The deposited film of thickness ~3 µm shows a coercivity of 268 kA/m, a remanence of 0.4 T and a maximum energy product of 35 kJ/m 3 in the out-of-plane direction. The variation in the hard-magnetic properties of the films for changing the film thickness is analyzed in terms of the composition, crystalline structure and grain size. As the thickness is increased from 0.9 µm to 26 µm, the in-plane coercivity reduces by 17% due to increase of grain size and Co content in the alloy structure. The in-plane squareness factor increases by 1.5 times as the thickness is increased over the above-mentioned range, which results in an enhancement of in-plane remanence value. The magnetization reversal behavior of the deposited films indicates that the nature of magnetic interaction is significantly influenced by the thickness of the films, where the dipolar interaction for the thinner films changes to exchange coupling at higher thickness due to increase of grain size. Finally, an innovative design strategy to integrate CoPtP in magnetic MEMS devices by micro-patterning is proposed and analyzed using finite element method. The demagnetization fields of the magnetic elements are minimized through optimized micro-patterned structures which improve the viability of PR deposited CoPtP micro-magnets having suitable nano-grains in potential MEMS based applications.
Key Processing and Characterization Issues, and Nanoscale Effects, 2016
With the seemingly inexorable increase in the use of devices designed to access the internet for ... more With the seemingly inexorable increase in the use of devices designed to access the internet for an ever increasing series of applications, there is a constant need for data storage technologies with higher densities, non-volatility and lower power consumption. 3 Single-phase, room temperature magnetoelectric multiferroic materials are of considerable interest for such applications. 4 The unique advantage of these advanced materials is that not only could they find application in high storage density, low-power memory devices that can be electrically written and magnetically read, but also by constructing devices that exploit the presence of both ferroelectric and ferromagnetic states, memory technologies with 4-state logic could be achieved 5-representing a clear improvement over current 2-state logic memory. However, materials that are both multiferroic and magnetoelectric at room temperature are very unusual. 6 In this chapter, we review approaches currently under investigation for the fabrication of single phase magnetoelectric multiferroics, from bulk ceramics to those in thin film form. We present This is the pre-peer reviewed version of the following article which has been published in final form at
In this article we reply to the concerns raised by Harres et al. [Phys. Rev. Lett. (to be publish... more In this article we reply to the concerns raised by Harres et al. [Phys. Rev. Lett. (to be published)] about some of the results reported in our original paper [T. Maity et al. Phys. Rev. Lett. 110, 107201 (2013)]. We show that the magnetic hysteresis loops are not minor and both path dependency of exchange bias and presence of superspin glass phase in the nanocomposite are indisputable.
We report the results of direct measurement of remanent hysteresis loops on nanochains of BiFeO3 ... more We report the results of direct measurement of remanent hysteresis loops on nanochains of BiFeO3 at room temperature under zero and ∼20 kOe magnetic field. We noticed a suppression of remanent polarization by nearly ∼40% under the magnetic field. The powder neutron diffraction data reveal significant ion displacements under a magnetic field which seems to be the origin of the suppression of polarization. The isolated nanoparticles, comprising the chains, exhibit evolution of ferroelectric domains under dc electric field and complete 180 o switching in switching-spectroscopy piezoresponse force microscopy. They also exhibit stronger ferromagnetism with nearly an order of magnitude higher saturation magnetization than that of the bulk sample. These results show that the nanoscale BiFeO3 exhibits coexistence of ferroelectric and ferromagnetic order and a strong magnetoelectric multiferroic coupling at room temperature comparable to what some of the type-II multiferroics show at a very low temperature.
We report the temperature-dependent Raman and dielectric spectroscopy of chemically synthesized B... more We report the temperature-dependent Raman and dielectric spectroscopy of chemically synthesized BiFeO 3 nanoparticles (average size ∼50-60 nm). The Raman spectra (90-700 K) show two sets of transitions in the lowest Raman E mode, associated with Bi-O bond motion situated in close proximity to the spin reorientation transitions reported for BiFeO 3 , thereby indicating the existence of possible coupling between magnons and phonons for particle size below the helical order parameter (62 nm). These transitions are slightly shifted in temperature in comparison to the bulk single crystals. We also observe a step-like behavior in Raman peak position around the Nèel temperature, suggesting that the phonons are influenced by the magnetic ordering in nanosized BiFeO 3. The heat-flow measurements show two sharp endothermic peaks at 1094 and 1223 K representing rhombohedral to orthorhombic or monoclinic transition followed by transition into the cubic phase above 1200 K. The low temperature (20-325 K), frequency-dependent (1-10 6 Hz) dielectric constant and loss tangent measurements show that the loss tangent (∼10-3) and ac conductivity values (∼10-8 Ohm-1cm-1) are orders of magnitude lower than the reported values for BiFeO 3 ceramics, indicating high levels of ionic purity of our samples. The real part of the permittivity shows a slight reduction in its value (∼30) in comparison to the bulk single crystals. Similar to the Stokes Raman shift, its temperature-dependent dielectric constant also shows four weak anomalies at ∼85, 168, 205, and 230 K situated in close proximity to the spin reorientation transitions, indicating magnetoelectric coupling.
Cupric oxide nanoparticles of∼ 8–10 nm width and 40–45 nm length self assembled as large particle... more Cupric oxide nanoparticles of∼ 8–10 nm width and 40–45 nm length self assembled as large particles∼ 1–1.5 μm have been investigated, in the 10–325 K temperature range, using magnetic and dielectric measurements. In magnetic measurements a single broad peak at∼ 230 K in a zero field cooled sample has been observed. Coercivity, in magnetization measurements at 10 K, suggests that the nanoparticles are core-shell type particles with an antiferromagnetic core and a ferromagnetic shell. Dielectric ...
Combined strain + doping method is used in a VAN system to realise exemplary properties which can... more Combined strain + doping method is used in a VAN system to realise exemplary properties which cannot be realised in plain films.
The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2... more The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2MnO3 (LCMO) thin films grown on two types of substrates, SrTiO3 (001) (STO) and LaAlO3 (001) (LAO) has been studied as a function of film thickness within the range of 25-300 nm. The STO substrate imposes an in-plane tensile biaxial strain while LAO substrate imposes an in-plane compressive biaxial strain. The in-plane biaxial strain on LCMO by STO substrate gets relaxed more rapidly than that by LAO substrate but both LCMO/STO and LCMO/LAO show a maximum entropy change (∆SM) of ∼ 12.
In this work, heteroepitaxial vertically aligned nanocomposite (VAN) La 0.9 Ba 0.1 MnO 3 (LBMO)-C... more In this work, heteroepitaxial vertically aligned nanocomposite (VAN) La 0.9 Ba 0.1 MnO 3 (LBMO)-CeO 2 films are engineered to produce ferromagnetic insulating (FMI) films. From combined X-ray photoelectron spectroscopy, X-ray diffraction, and electron microscopy, the elimination of the insulator−metal (I−M) transition is shown to result from the creation of very small lateral coherence lengths (with the corresponding lateral size ∼ 3 nm (∼7 u.c.)) in the LBMO matrix, achieved by engineering a high density of CeO 2 nanocolumns in the matrix. The small lateral coherence length leads to a shift in the valence band maximum and reduction of the double exchange (DE) coupling. There is no "dead layer" effect at the smallest achieved lateral coherence length of ∼3 nm. The FMI behavior obtained by lateral dimensional tuning is independent of substrate interactions, thus intrinsic to the film itself and hence not related to film thickness. The unique properties of VAN films give the possibility for multilayer spintronic devices that can be made without interface degradation effects between the layers.
Magnetoelectric systems could be used to develop magnetoelectric random access memory and microse... more Magnetoelectric systems could be used to develop magnetoelectric random access memory and microsensor devices. One promising system is the two-phase 3-1-type multiferroic nanocomposite in which a one-dimensional magnetic column is embedded in a three-dimensional ferroelectric matrix. However, it suffers from a number of limitations including unwanted leakage currents and the need for biasing with a magnetic field. Here we show that the addition of an antiferromagnet to a 3-1-type multiferroic nanocomposite can lead to a large, self-biased magnetoelectric effect at room temperature. Our three-phase system is composed of a ferroelectric Na0.5Bi0.5TiO3 matrix in which ferrimagnetic NiFe2O4 nanocolumns coated with antiferromagnetic p-type NiO are embedded. This system, which is self-assembled, exhibits a magnetoelectric coefficient of up to 1.38 × 10–9 s m–1, which is large enough to switch the magnetic anisotropy from the easy axis (Keff = 0.91 × 104 J m–3) to the easy plane (Keff = –1.65 × 104 J m–3). A three-phase system that is composed of a ferroelectric Na0.5Bi0.5TiO3 matrix in which ferrimagnetic NiFe2O4 nanocolumns coated with antiferromagnetic p-type NiO are embedded exhibits self-biased magnetoelectric switching at room temperature.
Goal To determine patient-reported financial and family burden associated with treatment of cance... more Goal To determine patient-reported financial and family burden associated with treatment of cancer in the previous 28 days across Canada. Methods A self-administered questionnaire (P-SAFE v7.2.4) was completed by 901 patients with cancer from twenty cancer centres nationally (344 breast, 183 colorectal, 158 lung, 216 prostate) measuring direct and indirect costs related to cancer treatment and foregone care. Monthly self-reported out-of-pocket-costs (OOPCs) included drugs, homecare, homemaking, complementary/ alternative medicines, vitamins/supplements, family care, accommodations, devices, and “other” costs. Travel and parking costs were captured separately. Patients indicated if OOPC, travel, parking, and lost income were a financial burden. Results Mean 28-day OOPCs were CA$518 (US Purchase Price Parity [PPP] $416), plus CA$179 (US PPP $144) for travel and CA$84 (US PPP $67) for parking. Patients self-reporting high financial burden had total OOPCs (33%), of CA$961 (US PPP $772),...
Orthorhombic RMnO3 (R = rare-earth cation) compounds are type-II multiferroics induced by inversi... more Orthorhombic RMnO3 (R = rare-earth cation) compounds are type-II multiferroics induced by inversion-symmetry-breaking of spin order. They hold promise for magneto-electric devices. However, no spontaneous room-temperature ferroic property has been observed to date in orthorhombic RMnO3. Here, using 3D straining in nanocomposite films of (SmMnO3)0.5((Bi,Sm)2O3)0.5, we demonstrate room temperature ferroelectricity and ferromagnetism with TC,FM ~ 90 K, matching exactly with theoretical predictions for the induced strain levels. Large in-plane compressive and out-of-plane tensile strains (−3.6% and +4.9%, respectively) were induced by the stiff (Bi,Sm)2O3 nanopillars embedded. The room temperature electric polarization is comparable to other spin-driven ferroelectric RMnO3 films. Also, while bulk SmMnO3 is antiferromagnetic, ferromagnetism was induced in the composite films. The Mn-O bond angles and lengths determined from density functional theory explain the origin of the ferroelectri...
Annually, thousands of individuals die and tens of thousands are hospitalized in association with... more Annually, thousands of individuals die and tens of thousands are hospitalized in association with suspected adverse drug reactions (ADRs) in Canada. We analyzed the reports from the Canada Vigilance Adverse Reaction online database and present a synopsis of the state of ADRs in Canada between 2009 and 2018. Our synopsis includes both cross-sectional and longitudinal insights into ADR demographics, outcomes, associated drugs and disease indications. In closing, we highlight five overarching issues uncovered in our analysis, which have potential implications for future policy formulation. Further in-depth exploration is required to shine some additional light on these issues.
Three-dimensional (3D) strain induced in self-assembled vertically aligned nanocomposite (VAN) ep... more Three-dimensional (3D) strain induced in self-assembled vertically aligned nanocomposite (VAN) epitaxial films provides an unrivaled method to induce very large strains in thin films. Here, by growing VAN films of EuTiO (ETO)-Eu O (EO) with different EO fractions, the vertical strain was systematically increased in ETO, up to 3.15%, and the Eu-Ti-Eu bond angle along <111> decreased by up to 1°, leading to a weakening of the antiferromagnetic interactions, and switching from antiferromagnetic to ferromagnetic behaviour. Our work has shown for the first time that Eu-Ti-Eu superexchange interactions play a key role in determining the magnetic ground state of ETO. More broadly, our work serves as an exemplar to show that multifunctionalities in strong spin-lattice coupling perovskite oxides can be uniquely tuned at the atomic scale using simple VAN structures.
The effect of interface roughness of ferromagnetic and antiferromagnetic layers on exchange bias ... more The effect of interface roughness of ferromagnetic and antiferromagnetic layers on exchange bias is still not well understood. In this report we have investigated the effect of surface roughness in (111)oriented antiferromagnetic CoO films on exchange bias with ferromagnetic Fe grown on top. The surface roughness is controlled at the atomic scale, over a range below ~ 0.35 nm, by varying layer thickness of the CoO films. It is observed that both exchange bias field (H E) and coercivity (H C) extensively depend on the atomic scale roughness of the CoO (111) at the interface with Fe film. An opposite dependence of H E and H C on interface roughness was found, which was ascribed to partially compensated spin states induced by the atomic roughness at the fully uncompensated CoO (111) surfaces and was corroborated using the Monte Carlo simulations. Moreover, the onset temperature for H C is found to be up to ~ 80 K below the blocking temperature (T B) and the temperature dependence-2-of H C follows the power law with a critical exponent equal to one, which indicates that, in this system, H C is more of an interface-related property than H E .
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
UCC Library and UCC researchers have made this item openly available. Please let us know how this... more UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Exploring ferroelectric and magnetic properties of Tb-substituted m = 5 layered Aurivillius phase thin films
UCC Library and UCC researchers have made this item openly available. Please let us know how this... more UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Magnetic properties of microwave-plasma (thermal) chemical vapour deposited Co-filled (Fe-filled) multiwall carbon nanotubes: comparative study for magnetic device applications
In this paper, the magnetic properties of Co-rich CoPtP films electrodeposited using an optimized... more In this paper, the magnetic properties of Co-rich CoPtP films electrodeposited using an optimized Pulse Reverse (PR) technique are investigated for magnetic MEMS applications. By using a combination of forward and reverse pulse with optimized duty cycles during deposition and suitable bath chemistry, the film stress is reduced significantly, which results in smooth, crack-free films of thickness up to 26 µm. The deposited film of thickness ~3 µm shows a coercivity of 268 kA/m, a remanence of 0.4 T and a maximum energy product of 35 kJ/m 3 in the out-of-plane direction. The variation in the hard-magnetic properties of the films for changing the film thickness is analyzed in terms of the composition, crystalline structure and grain size. As the thickness is increased from 0.9 µm to 26 µm, the in-plane coercivity reduces by 17% due to increase of grain size and Co content in the alloy structure. The in-plane squareness factor increases by 1.5 times as the thickness is increased over the above-mentioned range, which results in an enhancement of in-plane remanence value. The magnetization reversal behavior of the deposited films indicates that the nature of magnetic interaction is significantly influenced by the thickness of the films, where the dipolar interaction for the thinner films changes to exchange coupling at higher thickness due to increase of grain size. Finally, an innovative design strategy to integrate CoPtP in magnetic MEMS devices by micro-patterning is proposed and analyzed using finite element method. The demagnetization fields of the magnetic elements are minimized through optimized micro-patterned structures which improve the viability of PR deposited CoPtP micro-magnets having suitable nano-grains in potential MEMS based applications.
Key Processing and Characterization Issues, and Nanoscale Effects, 2016
With the seemingly inexorable increase in the use of devices designed to access the internet for ... more With the seemingly inexorable increase in the use of devices designed to access the internet for an ever increasing series of applications, there is a constant need for data storage technologies with higher densities, non-volatility and lower power consumption. 3 Single-phase, room temperature magnetoelectric multiferroic materials are of considerable interest for such applications. 4 The unique advantage of these advanced materials is that not only could they find application in high storage density, low-power memory devices that can be electrically written and magnetically read, but also by constructing devices that exploit the presence of both ferroelectric and ferromagnetic states, memory technologies with 4-state logic could be achieved 5-representing a clear improvement over current 2-state logic memory. However, materials that are both multiferroic and magnetoelectric at room temperature are very unusual. 6 In this chapter, we review approaches currently under investigation for the fabrication of single phase magnetoelectric multiferroics, from bulk ceramics to those in thin film form. We present This is the pre-peer reviewed version of the following article which has been published in final form at
In this article we reply to the concerns raised by Harres et al. [Phys. Rev. Lett. (to be publish... more In this article we reply to the concerns raised by Harres et al. [Phys. Rev. Lett. (to be published)] about some of the results reported in our original paper [T. Maity et al. Phys. Rev. Lett. 110, 107201 (2013)]. We show that the magnetic hysteresis loops are not minor and both path dependency of exchange bias and presence of superspin glass phase in the nanocomposite are indisputable.
We report the results of direct measurement of remanent hysteresis loops on nanochains of BiFeO3 ... more We report the results of direct measurement of remanent hysteresis loops on nanochains of BiFeO3 at room temperature under zero and ∼20 kOe magnetic field. We noticed a suppression of remanent polarization by nearly ∼40% under the magnetic field. The powder neutron diffraction data reveal significant ion displacements under a magnetic field which seems to be the origin of the suppression of polarization. The isolated nanoparticles, comprising the chains, exhibit evolution of ferroelectric domains under dc electric field and complete 180 o switching in switching-spectroscopy piezoresponse force microscopy. They also exhibit stronger ferromagnetism with nearly an order of magnitude higher saturation magnetization than that of the bulk sample. These results show that the nanoscale BiFeO3 exhibits coexistence of ferroelectric and ferromagnetic order and a strong magnetoelectric multiferroic coupling at room temperature comparable to what some of the type-II multiferroics show at a very low temperature.
We report the temperature-dependent Raman and dielectric spectroscopy of chemically synthesized B... more We report the temperature-dependent Raman and dielectric spectroscopy of chemically synthesized BiFeO 3 nanoparticles (average size ∼50-60 nm). The Raman spectra (90-700 K) show two sets of transitions in the lowest Raman E mode, associated with Bi-O bond motion situated in close proximity to the spin reorientation transitions reported for BiFeO 3 , thereby indicating the existence of possible coupling between magnons and phonons for particle size below the helical order parameter (62 nm). These transitions are slightly shifted in temperature in comparison to the bulk single crystals. We also observe a step-like behavior in Raman peak position around the Nèel temperature, suggesting that the phonons are influenced by the magnetic ordering in nanosized BiFeO 3. The heat-flow measurements show two sharp endothermic peaks at 1094 and 1223 K representing rhombohedral to orthorhombic or monoclinic transition followed by transition into the cubic phase above 1200 K. The low temperature (20-325 K), frequency-dependent (1-10 6 Hz) dielectric constant and loss tangent measurements show that the loss tangent (∼10-3) and ac conductivity values (∼10-8 Ohm-1cm-1) are orders of magnitude lower than the reported values for BiFeO 3 ceramics, indicating high levels of ionic purity of our samples. The real part of the permittivity shows a slight reduction in its value (∼30) in comparison to the bulk single crystals. Similar to the Stokes Raman shift, its temperature-dependent dielectric constant also shows four weak anomalies at ∼85, 168, 205, and 230 K situated in close proximity to the spin reorientation transitions, indicating magnetoelectric coupling.
Cupric oxide nanoparticles of∼ 8–10 nm width and 40–45 nm length self assembled as large particle... more Cupric oxide nanoparticles of∼ 8–10 nm width and 40–45 nm length self assembled as large particles∼ 1–1.5 μm have been investigated, in the 10–325 K temperature range, using magnetic and dielectric measurements. In magnetic measurements a single broad peak at∼ 230 K in a zero field cooled sample has been observed. Coercivity, in magnetization measurements at 10 K, suggests that the nanoparticles are core-shell type particles with an antiferromagnetic core and a ferromagnetic shell. Dielectric ...
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Papers by Tuhin Maity