Browsing by Author "Surajit Ghosh"

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Antiferromagnetic coupling in Co-doped ZnS
(Kluwer Academic Publishers, 2015) Prayas Chandra Patel; Surajit Ghosh; P.C. Srivastava
In this paper, we report room-temperature ferromagnetism in chemically synthesized Zn1−xCoxS (0 ≤ x ≤ 0.10) diluted magnetic semiconductor nanoparticles of ~3–5 nm. The incorporation of Co2+ ion for Zn2+ ions in ZnS lattice and the particle size were confirmed by XRD and TEM along with selected area electron diffraction analysis. UV–Vis measurement showed reduction in the bandgap energy with the increase in Co doping. Maximum magnetization was observed for samples with x = 0.04. From photoluminescence, spectra luminescence efficiency was found to get enhanced on Co doping. Magnetization behavior can be understood to be due to defect-induced ferromagnetism; however, for higher doping concentration, the antiferromagnetic coupling of Co–Co interaction in the close proximity results in the decrease of the overall magnetization of the samples. Moreover, magneto-electronic study also showed a maximum negative magneto-resistance of ~43 % for x = 0.04. © 2015, Springer Science+Business Media New York.
B-site disorder driven multiple-magnetic phases: Griffiths phase, re-entrant cluster glass, and exchange bias in Pr2CoFeO6
(American Institute of Physics Inc., 2019) Arkadeb Pal; Prajyoti Singh; V.K. Gangwar; Surajit Ghosh; P. Prakash; S.K. Saha; Amitabh Das; Manoranjan Kumar; A.K. Ghosh; Sandip Chatterjee
The magnetic spin ordering and the magnetization dynamics of a double perovskite Pr2CoFeO6 have been investigated by employing the (dc and ac) magnetization and neutron powder diffraction techniques. The study revealed that Pr2CoFeO6 adopted a B-site disordered orthorhombic structure (Pnma). Furthermore, ab initio band structure calculations suggested an insulating antiferromagnetic ground state. Magnetization measurements revealed that the system possesses a spectrum of competing magnetic phases, viz., long range canted antiferromagnetic (AFM) spin ordering (TN ∼269 K), Griffiths-like phase, re-entrant cluster glass (TG ∼34 K), and exchange bias effects. The neutron diffraction study divulged the exhibition of a long range G-type of canted AFM spin ordering. The random nonmagnetic dilution of magnetic Fe3+ (high spin) ions by Co3+ (low spin) ions due to B-site disorder essentially played a crucial role in manifesting such magnetic properties of the system. © 2019 Author(s).
Bound magnetic polaron driven room-temperature ferromagnetism in Ni doped ZnS nanoparticles
(Elsevier Ltd, 2018) Prayas Chandra Patel; Surajit Ghosh; P.C. Srivastava
Magnetism in dilute magnetic semiconductors (DMSs) has been a controversial topic since its discovery. There are many models which predict the origin of room temperature ferromagnetism (RTFM) in TM doped wide band gap semiconductors. Here, we report RTFM in chemically synthesized cubic Zn1-xNixS (0 ≤ x ≤ 0.08) DMS nanoparticles of ∼3–5 nm size. Ferromagnetic behavior (at 300 K and 5 K) was found to increase with the increase in Ni doping concentration and was understood due to defect induced ferromagnetism. The low temperature magnetization measurement (ZFC-FC) shows that the nanoparticles are strongly coupled by magnetic interactions. Optical studies showed decrease in the energy bandgap along with the presence of sulfur and zinc vacancies and surface defects. Low temperature resistivity measurement depicted the semiconducting nature of the synthesized samples. With increase in doping concentration, an increase in the resistive behavior was observed which was explained in the realm of defects states created due to doping of the Ni ions. © 2018 Elsevier B.V.
Effect of f–d and d–d Interactions on Dielectric and Optical Properties of Pyrochlore Eu2−xFexTi2O7
(John Wiley and Sons Inc, 2022) Mohd Alam; Arkadeb Pal; Surajit Ghosh; Ranjan K. Singh; Anup K. Ghosh; Sandip Chatterjee
X-ray diffraction, Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, dielectric property, and UV–vis spectroscopy studies of pyrochlore Eu2−xFexTi2O7 have been performed. The X-ray pattern shows that Eu2−xFexTi2O7 has a pure pyrochlore phase up to x = 0.2. The structural analysis shows a strong distortion of TiO6 octahedral due to the presence of the interstitial anionic vacant site. A significantly increased band intensity of FTIR spectrum with Fe doping suggests the enhanced anionic disorder in the system. The broadening of Raman peaks with increasing x supports the increased disorder in TiO6 octahedral. Dielectric study of Eu2Ti2O7 shows a diffused dielectric transition below 150 K. The dielectric diffusiveness and transition temperature get enhanced with Fe doping due to enhanced anionic distortion. The dielectric constant of Eu2−xFexTi2O7 is also increased on Fe doping. The UV–vis spectrum exhibits a strong absorbance in the UV region and a redshift with Fe doping. The Tauc plot of UV–vis spectrum shows multiple successive valence band edges and the bandgap gets reduced with Fe doping due to the formation of new interbands. Thus, these materials are interesting for people searching for material to be used in tunable electrical and optical devices. © 2022 Wiley-VCH GmbH.
Effect of impurity concentration on optical and magnetic properties in ZnS:Cu nanoparticles
(Elsevier B.V., 2017) Prayas Chandra Patel; Surajit Ghosh; P.C. Srivastava
To obtain enhanced room temperature ferromagnetism (RTFM) along with the increase in optical bandgap in the compound semiconductors has been an interesting topic. Here, we report RTFM along with increase in energy bandgap in chemically synthesized Zn1−xCuxS (0 ≤ x ≤ 0.04) DMS nanoparticles. Structural properties of the synthesized samples studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the formation of cubic phase Cu doped ZnS nanoparticles of ~3–5 nm size. An intrinsic weak ferromagnetic behavior was observed in pure ZnS sample (at 300 K) which got increased in Cu doped samples and was understood due to defect induced ferromagnetism. UV–vis measurement showed increase in the energy bandgap with the increase in Cu doping. The PL study suggested the presence of sulfur and zinc vacancies and surface defects which were understood contributing to the intrinsic FM behavior. © 2017 Elsevier B.V.
Electronic structure by X-ray absorption spectroscopy and observation of field induced unusually slow spin relaxation from magnetic properties in pyrochlore Eu2−xFexTi2O7
(Elsevier B.V., 2019) Arkadeb Pal; Surajit Ghosh; Shiv Kumar; Eike F. Schwier; Masahiro Sawada; Kenya Shimada; Mukul Gupta; D.M. Phase; A.K. Ghosh; Sandip Chatterjee
X-ray absorption spectroscopy (XAS) and magnetization of hybrid pyrochlore Eu2-xFexTi2O7 (EFTO) were investigated, where the rare earth Eu (4f) was replaced with transition metal Fe (3d) to introduce competing 4f-3d interactions. It is confirmed that the valence states of Eu and Fe ions are formally trivalent while that of Ti ions are tetravalent (3d0). The analysis yielded that the tetravalent Ti ions occupy octahedral sites with distorted Oh symmetry which is triggered by the presence of vacant 8a anionic site adjacent to TiO6 octahedra. Further study with Fe doping revealed that it essentially reduces the octahedral distortion by introducing anionic disorder (migration of 48f oxygen ions to 8a site). Analysis of O K edge XAS spectra further confirmed the Fe substitution causing the systematic change in the ligand (O2−) coordination of the Ti4+ cations. Interestingly, a new field induced transition at low temperature T* (4 K < T* < 8 K) associated with unusually slow spin relaxation was observed. The transition shifted towards higher temperatures both with increasing applied field and Fe concentration. However, the single ion spin freezing (Tf ∼ 35 K) appears to be largely suppressed with Fe substitution. Moreover, dc magnetization data showed rise of ferromagnetic contribution below 100 K. © 2018
Enhanced Photocatalytic Activity and Low Temperature Magnetic/Transport Study of Cu-Doped ZnS-Based Diluted Magnetic Semiconductor Nanoparticles
(Springer New York LLC, 2019) Prayas Chandra Patel; Surajit Ghosh; Pankaj Kumar Mishra; P.C. Srivastava
Diluted magnetic semiconductors (DMSs), having interesting magnetic/transport properties, are currently being explored in photocatalytic application as well. This report presents photocatalytic and low temperature magnetic/transport study of chemically synthesized 3-5 nm sized cubic Zn1-xCuxS (0 ≤ x ≤ 0.04) DMS nanoparticles. Both studies have their own importance, former relates to dye degradation, while later attempts to understand origin of magnetic behavior in DMSs (which is still debatable). As a photocatalyst, Cu doped ZnS NPs showed enhanced degradation-efficiency for methylene blue dye. Magnetization study showed enhanced magnetic moment in Cu doped samples, which in the low temperature regime got further enhanced and was understood due to defect induced ferromagnetism. Low temperature transport study showed the decrease in resistivity of the Cu doped samples and was understood in terms of defects states created due to doping of the Cu ions and governed by conduction mechanism, namely thermal activation and variable range hopping. © 2019, The Minerals, Metals & Materials Society.
Existence of exchange bias and Griffith phase in (Tb1-xCex)MnO3
(Elsevier B.V., 2020) Surajit Ghosh; Abhishek Kumar; Arkadeb Pal; Prajyoti Singh; Prince Gupta; Khyati Anand; U.K. Gautam; A.K. Ghosh; Sandip Chatterjee
The structural and magnetic properties of (Tb1-xCex)MnO3 have been investigated. The presence of Griffith's phase has been confirmed from the AC susceptibility study of the materials. The observed Griffith phase in (Tb1-xCex)MnO3 is attributed to the exchange interaction between Mn3+/Mn2+ ions. Chemical analysis by X-ray photo-emission spectroscopy has shown the presence of mix valence state of Mn and oxygen vacancy in the materials. At low temperatures, the materials also show existence of exchange bias in field cooled condition which changes with Ce content. Jahn-Teller distortion and oxygen vacancy are found to dominate in these systems to change the Mn–O–Mn bond angle which in turn induce canted antiferromagnetism (AFM) in this system. The canted AFM plays an important role in getting the exchange bias effect. © 2019 Elsevier B.V.
Extraordinary magnetic properties of double perovskite Eu2CoMnO6wide band gap semiconductor
(Institute of Physics Publishing, 2020) Mohd Alam; Prajyoti Singh; Khyati Anand; Arkadeb Pal; Surajit Ghosh; A.K. Ghosh; Ranjan K. Singh; Amish G. Joshi; Sandip Chatterjee
Some novel magnetic behaviours in double perovskite Eu2CoMnO6 (ECMO) have been reported. The x-ray photoemission spectroscopy study shows the presence of mixed valence states of transition metal ions. The UV-visible absorption spectroscopic study suggests that the ECMO has a direct wide band gap. A second-order magnetic phase transition as a sudden jump in the magnetization curve has been observed around 124.5 K. The large bifurcation between the zero field cooling and field cooling, suggests existence of strong spin frustration in the system. The inverse DC susceptibility confirms the presence of the Griffiths like phase. Sharp steps in magnetization have been observed in the M-H curve at 2 K, which vanishes on increasing temperature. The AC susceptibility study demonstrates the Hopkinson like effect as well as the presence of volume spin-glass-like behaviour. The temperature dependent Raman spectrum shows the presence of spin-phonon coupling. © 2020 IOP Publishing Ltd.
Hysteresis in magnetoresistance and formation of spin glass like structure in PVA capped Fe3O4
(Springer New York LLC, 2017) Surajit Ghosh; Prayas Chandra Patel; P.C. Srivastava
Here, we report the temperature dependent hysteresis in the magneto transport in PVA capped Fe3O4 nanoparticles. The synthesis of the nanoparticles of size 10–15 nm were carried out via co-precipitation method followed by heat treatment at different temperatures. Structural studies confirm the formation of polycrystalline Fd 3 ¯ m phase of Fe3O4 when the samples were sintered up to 600 °C. FTIR studies show that PVA and magnetic grains were attached through hydrogen bonding between hydroxyl group of PVA and protonated surface of the oxide. Spin glass type transition was observed in the ZFC–FC plots at 125 K which is also the Verwey transition temperature TV as measured from the transport studies. A hysteresis in the MR plot was found which was explained in the realm of tunnel transport through ferromagnetic grain and antiferromagnetic surface of the ferrite particles. Tunnelling through the dielectric spacer layer of PVA has an overall impact to increase the resistance of the samples. The temperature dependence of the hysteresis gives a major hint to the origin of the spin glass type behaviour of the samples. © 2017, Springer Science+Business Media, LLC.
In vitro concentration dependent detection of creatinine: a surface enhanced Raman scattering and fluorescence study
(Royal Society of Chemistry, 2016) Debraj Gangopadhyay; Poornima Sharma; Rajib Nandi; Moumita Das; Surajit Ghosh; Ranjan K. Singh
An attempt has been made to detect the concentration of creatinine in a very dilute aqueous solution in vitro on the basis of the Jaffe reaction, the commonly used reaction for clinical determination of creatinine concentration in blood serum or urine. For this various spectroscopic techniques viz. Raman spectroscopy, surface enhanced Raman scattering, UV-visible and fluorescence spectroscopy have been used. As a result of the Jaffe reaction using aqueous solutions of creatinine at different concentrations and picric acid and NaOH as reagents, a reddish orange colored Jaffe complex is produced. The concentration dependent SERS spectra of the Jaffe complex show gradual decrease in the intensity of ring deformation mode of creatinine on decreasing creatinine concentration. The concentration dependent absorption spectra of the Jaffe complex show changes in intensity in one of the absorption peaks characteristic of creatinine. The concentration dependent fluorescence emission spectra of the Jaffe complex show a blue shift in emission maxima on reducing the concentration of creatinine in the solution. The observed results suggest the possibility to detect the concentration of creatinine in a very dilute solution in vitro by SERS and fluorescence techniques and the application of these techniques in vivo might aid in a more specific and accurate determination of creatinine in serum or urine. © The Royal Society of Chemistry.
Injecting electrode controlled electronic transport across Fe 3O4 film-Si interfacial structure
(Elsevier Ltd, 2014) Surajit Ghosh; Neelabh Srivastava; P.C. Srivastava
A study of electronic transport has been carried out across a half-metallic Fe3O4 film-nSi interfacial structure in CPP mode with an interfacial SiO2 layer of <5 nm. It has been measured with and without applied magnetic field along the plane of the interface between 25 K and 300 K to investigate the role of half-metallic Fe3O4 layer on the transport. The electronic transport has shown a distinct behaviour for the reverse bias in which injection takes place from metallic film of Fe3O4 to silicon than for the forward bias in which injection takes place from silicon to metallic Fe3O4 side. It has been found that the reverse bias current shows a tunnel transport, Verwey transition like feature and low temperature positive GMR, evidencing spin involved transport from Fe3O4 to semiconductor side. Whereas the forward bias current has not shown any of the above features but a thermionic controlled transport, showing a change of resistance with temperature as of semiconductor silicon. Thus, it has been found that the transport is controlled by physical properties of the injecting electrode. The study has shown that the transport below Verwey transition temperature (TV) for the Fe3O4 film interfacial structure is also related to its electronic spins. The observed GMR of ∼200% at low temperature (for reverse bias current only) has been discussed as the effect of electronic spin scattering. Our unique observations from simple measurements of CPP I-V across the interfacial structure of Fe3O4-nSi seem significant to reveal that the Verwey transition is related to spins of half-metallic Fe 3O4. © 2014 Elsevier Inc. All rights reserved.
Interface States of Fe3O4/Si interfacial structure and effect of magnetic field
(Springer Science and Business Media, LLC, 2014) Surajit Ghosh; P.C. Srivastava
Electronic transport across Fe3O4/Si interfacial structure has been studied with and without the application of magnetic fields along the interfacial plane, up to 8 kG. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics across the junction have been recorded for various bias voltages, frequency and magnetic field. The interfacial parameters, such as, ideality factor (n), barrier height (B0), series resistance (R S) and donor concentration (N D) etc. have been estimated from the characteristics. The interface state density (N SS) and their energy distribution have been estimated by using the interfacial parameters. It has been observed that the N SS decreases as the energy increases from the conduction band edge towards the valence band. A magnetoresistance (MR) of ≥40% has been estimated from the I-V-H data along with its variation with magnetic field. The change of interface state density with the magnetic field shows a similar variation as MR versus H. From the observed variations, the interface states seem to be related to electronic spins. The possibility of an interfacial magnetic silicide or magnetic ions in the interfacial region has been invoked for the observed interface states. © 2014 The Minerals, Metals & Materials Society.
Interplay of spin, phonon, and lattice degrees in a hole-doped double perovskite: Observation of spin-phonon coupling and magnetostriction effect
(American Institute of Physics Inc., 2022) Arkadeb Pal; Khyati Anand; Neha Patel; Amitabh Das; Surajit Ghosh; Peter Tsung-Wen Yen; Shin-Ming Huang; R.K. Singh; H.D. Yang; A.K. Ghosh; Sandip Chatterjee
Unlike a typical spin-phonon coupling, an exhibition of unconventional spin-phonon coupling, which is mediated via magnetostriction effect, is reported in a hole-doped double perovskite Pr1.5Sr0.5CoMnO6. Various investigations including electronic and crystal structures, spin structure, transport property, lattice dynamics, and theoretical density of states analysis by density-functional theory (DFT) have been performed. A substantial increase in the mean oxidation states of Co ions and a concurrent abrupt decrease in the resistivity upon Sr doping is observed, thus altering its underlying transport mechanism. An insulating and ferromagnetic (FM) ground state is predicted by DFT calculations. The neutron diffraction data analysis reveals a complex crystal structure of Pr1.5Sr0.5CoMnO6, which consists of B-site disordered monoclinic (P21/n) and orthorhombic (Pnma) structures, highlighting the presence of an anti-site disorder in the system. The analysis also suggests an overall FM ordering of Co/Mn spins below 150 K for the monoclinic phase, whereas no such magnetic ordering is found for the orthorhombic phase. More interestingly, the neutron powder diffraction study perceives the presence of a strong magnetostriction effect in the system. Raman spectroscopy unravels the presence of a spin-phonon coupling, which is essentially mediated by the magnetostriction effect. © 2022 Author(s).
Investigation of multi-mode spin-phonon coupling and local B-site disorder in Pr2CoFeO6 by Raman spectroscopy and correlation with its electronic structure by XPS and XAS studies
(Institute of Physics Publishing, 2019) Arkadeb Pal; Surajit Ghosh; Amish G. Joshi; Shiv Kumar; Swapnil Patil; Prince K. Gupta; Prajyoti Singh; V.K. Gangwar; P. Prakash; Ranjan K. Singh; Eike F. Schwier; M. Sawada; K. Shimada; A.K. Ghosh; Amitabh Das; Sandip Chatterjee
Electronic structure of Pr2CoFeO6 (at 300 K) was investigated by x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy techniques. All three cations, i.e. Pr, Co and Fe were found to be trivalent in nature. XPS valance band analysis suggested the system to be insulating in nature. The analysis suggested that Co3+ ions exist in low spin state in the system. Moreover, Raman spectroscopy study indicated the random distribution of the B-site ions (Co/Fe) triggered by same charge states. In temperature-dependent Raman study, the relative heights of the two observed phonon modes exhibited anomalous behaviour near magnetic transition temperature TN ∼ 270 K, thus indicating towards interplay between spin and phonon degrees of freedom in the system. Furthermore, clear anomalous softening was observed below TN which confirmed the existence of strong spin-phonon coupling occurring for at least two phonon modes of the system. The line width analysis of the phonon modes essentially ruled out the role of magnetostriction effect in the observed phonon anomaly. The investigation of the lattice parameter variation across TN (obtained from the temperaturedependent neutron diffraction measurements) further confirmed the existence of the spin- phonon coupling. © 2019 IOP Publishing Ltd Printed in the UK.
Investigation of scale dependence and geomorphic stages of evolution through hypsometric analysis: a case study of Sirsa basin, western Himalaya, India
(Taylor and Francis Ltd., 2014) Pratik Dash; S.P. Aggarwal; Narender Verma; Surajit Ghosh
Hypsometric analysis is an important tool to identify and justify the erosional status, erosional processes, geologic and tectonic influences, and stage of landscape development of a basin. In this study, scale dependence of hypsometric integral (Ea) and hypsometric curve parameters were derived and analysed for various order sub-basins of Sirsa river. Here, Ea of higher order sub-basins are quite scale dependent and controlled by lithology; albeit Ea of all order sub-basins is independent of tectonic uplift. Based on Ea, all fourth and fifth order sub-basins were categorised in three classes. The analysis of hypsometric curve parameters showed that sub-basins of first category (Ea < 0.35) is characterised by upward-concave curve, fluvial process dominated and early old stage landscape. Sub-basins of second category (0.35 < Ea < 0.45) reflects concave-convex curve, dominance of fluvial process and mature landscape; whereas third category sub-basins (Ea > 0.45) are diffusive process dominated and belong to late youth to early mature stage. © 2013 Taylor & Francis.
Reentrant double glassy states and simultaneous presence of short- and long-range ordering in metamagnetic Co-doped Bi0·5La0·5Fe0·5Mn0·5O3 multiferroic
(Elsevier Masson s.r.l., 2022) Prince K. Gupta; Khyati Anand; Mohd Alam; Surajit Ghosh; Seema Kumari; Arkadeb Pal; Mahima Singh; K.K. Shukla; Peter Tsung-Wen Yen; Shin-Ming Huang; A.K. Ghosh; Sandip Chatterjee
A study of the structural and magnetic properties of Bi0·5La0·5Fe0·45Co0·05Mn0·5O3 is presented in the article. We report the rare observations of two glassy transitions below the long-range ordering temperature along with the metamagnetic transitions at low temperatures. Frequency and DC field dependence of AC susceptibility and isothermal relaxation of remnant magnetization studies have all shown the slow spin dynamics for the compound. Interestingly, in the glass phase of the materials, metamagnetic transitions of the antiferromagnetic spins were found which indicate the coexistence of the long-range ordered phase along with the short-range ordered glassy phase. The double cluster glass phases can be comprehended, from the relaxations of the spin clusters arising from the competing magnetic interactions present in the system. Moreover, the roles of additional exchange interactions which are brought to the system by Co doping are also considered in explaining the observed double cluster glass transitions. © 2022 Elsevier Masson SAS
Relaxor-super-paraelectric behaviour and crystal-field-driven spin-phonon coupling in pyrochlore Eu2Ti2O7
(IOP Publishing Ltd, 2022) Mohd Alam; Arkadeb Pal; Khyati Anand; Surajit Ghosh; Saurabh Tripathi; Ranjan K. Singh; A.K. Ghosh; H.D. Yang; Sandip Chatterjee
The temperature-dependent Raman spectroscopy and dielectric property of pyrochlore Eu2Ti2O7 have been investigated. The appearance of additional phonon modes below 200 K is observed suggesting a local structural change. The anomalous softening of the phonon modes and existence of crystal-field-induced short-range magnetic ordering below 150 K unveiled the possible spin-phonon coupling. The signature behaviour of a dipolar glassy-relaxor state and super-paraelectric nature has been demonstrated. Additional dielectric anomaly at lower temperature, below 40 K, related to spin-spin correlation has also been reported. © 2022 EPLA
Roles of Re-entrant cluster glass state and spin-lattice coupling in magneto-dielectric behavior of giant dielectric double perovskite La1.8Pr0.2CoFeO6
(Institute of Physics Publishing, 2020) Prajyoti Singh; Mohd Alam; Shiv Kumar; Khyati Anand; Vinod K. Gangwar; Surajit Ghosh; M. Sawada; K. Shimada; R.K. Singh; A.K. Ghosh; Sandip Chatterjee
La based Co-Fe combined double perovskite (La1.8Pr0.2CoFeO6) was synthesized and the dielectric (zero-field and in-field), magnetic, X-ray absorption and Raman spectroscopy measurements have been investigated for La1.8Pr0.2CoFeO6 double perovskite. The existence of re-entrant cluster glass state is observed. The magneto-dielectric (MD) is found in two temperature regions (25-80 K and 125-275 K). It has been demonstrated that the observed MD at low and high temperatures are respectively due to the spin freezing and the spin-lattice coupling. Furthermore, the very large dielectric constant and the low loss suggest that La1.8Pr0.2CoFeO6 is very important from the application point of view. © 2020 IOP Publishing Ltd.
Room temperature exchange bias in antiferromagnetic composite BiFeO3-TbMnO3
(American Institute of Physics Inc., 2019) Prince K. Gupta; Surajit Ghosh; Shiv Kumar; Arkadeb Pal; Prajyoti Singh; Mohd Alam; Abhishek Singh; Somnath Roy; Rahul Singh; Bheeshma Pratap Singh; N. Naveen Kumar; Eike F. Schwier; Masahiro Sawada; Takeshi Matsumura; Kenya Shimada; Hong-Ji Lin; Yi-Ying Chin; A.K. Ghosh; Sandip Chatterjee
The magnetic property of a 0.7BiFeO3-0.3TbMnO3 composite has been studied in detail and compared with that of 0.8BiFeO3-0.2TbMnO3. The magnetic properties in 0.7BiFeO3-0.3TbMnO3 are improved in manifold compared to BiFeO3. An exchange bias (HEB) is observed in both the compositions of these antiferromagnetic composites, which varies between 5 and 180 Oe with a maximum at ∼275 K. Isothermal remanent magnetization measurements at room temperature indicate the presence of an interfacial layer of a 2-dimensional dilute uniaxial antiferromagnet in a uniform magnetic field (2D DAFF). The presence of exchange bias can be explained on the basis of a strong strain-mediated magnetoelectric coupling induced exchange interaction and the creation of a 2D DAFF layer at the interface. The properties of this layer are defined by canting and pinning of BiFeO3 spins at the interface with TbMnO3 due to Fe and Mn interaction. X-ray magnetic circular dichroism confirms the presence of canted antiferromagnetic ordering of BiFeO3, charge transfer between Mn ions, and different magnetically coupled layers that play a vital role in the exchange bias. © 2019 Author(s).