Browsing by Author "Mohd Alam"

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Anharmonic phonon interactions and the Kondo effect in a FeSe/Sb2Te3/FeSe heterostructure: a proximity effect between ferromagnetic chalcogenide and di-chalcogenide
(Royal Society of Chemistry, 2022) Labanya Ghosh; Mohd Alam; Mahima Singh; Srishti Dixit; Satya Vijay Kumar; Abhineet Verma; Prashant Shahi; Yoshiya Uwatoko; Satyen Saha; Archana Tiwari; Ajay Tripathi; Sandip Chatterjee
In this report, we have introduced magnetic ordering into the nontrivial system of conventional topological insulators (TIs) by creating magnetic interfaces. In this context, antimony di-chalcogenide Sb2Te3 sandwiched between two thin layers of FeSe was prepared using the pulsed laser deposition (PLD) technique. The prepared heterostructure demonstrated good crystallinity along with homogeneous morphology displaying pyramid-shaped characteristic triangular islands. To comprehend the temperature and magnetic field modulated inter-layer properties of the prepared hetero-structure, transport, magneto-transport and magnetic properties were investigated. These properties establish the signature of the Kondo effect below 15 K, which has been attributed to the antiferromagnetic spin alignment in that temperature range. At around 150 K, longitudinal and transverse resistivity shows the metal-semiconductor transition, which was further elucidated through the anharmonic decay model in vibration phonon modes using Raman spectroscopy. Furthermore, a significant local spin evolution was explored at around 475 K by studying the magnetic properties of the system. The temperature dependency of the Raman modes confirmed the spin-phonon coupling initiated by local charge ordering at the proximity of the interface in the prepared hetero-structure. © 2022 The Royal Society of Chemistry.
B-site order/disorder in A2BB′O6 and its correlation with their magnetic property
(Institute of Physics, 2023) Mohd Alam; Sandip Chatterjee
The disorder in any system affects their physical behavior. In this scenario, we report the possibility of disorder in A2BB′O6 oxides and their effect on different magnetic properties. These systems show anti-site disorder by interchanging B and B′ elements from their ordered position and giving rise to an anti-phase boundary. The presence of disorder leads to a reduction in saturation M and magnetic transition temperature. The disorder prevents the system from sharp magnetic transition which originates short-range clustered phase (or Griffiths phase) in the paramagnetic region just above the long-range magnetic transition temperature. Further, we report that the presence of anti-site disorder and anti-phase boundary in A2BB′O6 oxides give different interesting magnetic phases like metamagnetic transition, spin-glass, exchange bias, magnetocaloric effect, magnetodielectric, magnetoresistance, spin-phonon coupling, etc. © 2023 IOP Publishing Ltd.
Coexistence of Kondo effect and Weak anti-localization in Topological insulator/Ferromagnetic heterostructure
(Elsevier B.V., 2024) Labanya Ghosh; Swayangsiddha Ghosh; Srishti Dixit; Mohd Alam; Neha Patel; Archana Tiwari; Prashant Shahi; Yoshiya Uwatoko; Sandip Chatterjee
The presence of a magnetic impurity in a topological insulator weakens the time-reversal symmetry by creating a limited gap at the Dirac point, and could result in the creation of new quantum states. On the other hand, causing magnetization in a topological insulator through the interlayer proximity effect to a magnetically ordered system is a better choice, as magnetic doping may have negative effects. In this report, the magnetic and magneto-transport properties of FeSe intercalated Bi2Se3 crystals and FeSe/Bi2Se3/FeSe hetero-structure have been investigated. The XPS depth profile was studied to confirm the layered structure of the hetero-structure. The weak anti-localization state in the multilayer system has been seen to coexist with the Kondo effect, which may have caused by the interfacial magnetic domains modifying the electronic characteristics at interfaces. Such magnetic spin-induced inter-layer coupling can be a pathway to room-temperature spintronic applications. © 2024
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.
Electrical and magnetic properties of double perovskite Y2-xCaxCoMnO6 (x = 0.1, 0.2, 0.5)
(Springer, 2024) Dheeraj Kumar; Mohd Alam; Prajyoti Singh; Srishti Dixit; A.K. Ghosh; Sandip Chatterjee
The crystal structure, electronic, magnetic, and transport properties of the hole substituted (Ca2+) and partially B-site disordered double perovskite Y2-xCaxCoMnO6 system are studied. At room temperature, the samples demonstrated a monoclinic perovskite structure with a space group P21/n which was confirmed by Rietveld refinement of X-ray diffraction data. Ultra-violet visible analysis of these samples shows a direct band gap including gap energy near about 1.50 eV. X-ray photoemission spectroscopy measurement shows that component Co and Mn ions exist in a mixed state (Co3+, Co2+, Mn3+, and Mn4+). All samples exhibit semiconducting/insulating, and electrical conduction can be explained by Mott’s 3-D variable range hopping and small polaron hopping fitting. The magnetization numerical value decreases observed with increases in Ca concentration appears to be caused by increases in antiferromagnetic (AFM) phases. The double perovskite Y1.9Ca0.1CoMnO6 and Y1.8Ca0.2CoMnO6 show ferromagnetic transition at transition temperatures Tc~ 70 K and Tc~ 68 K, respectively. The analysis of the samples’ zero fields cooled DC magnetic susceptibility as a function of temperature reveals Griffiths-like singularity features that arise as the concentration of Ca increases in the parent system. The Griffith-like phase exists in the sample Y-site with Ca-substitution is independent of the structural disorder caused by the John–Teller active Mn3+ions in sample Y1.5Ca0.5CoMnO6. Field-dependent magnetization shows meta-magnetic behavior at low-temperature regions in Y1.9Ca0.1CoMnO6 and Y1.8Ca0.2CoMnO6. As the concentration of Ca increased from Y1.8Ca0.2CoMnO6 to Y1.5Ca0.5CoMnO6 meta-magnetic behavior disappeared. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.
Enhancement of Multiferroic and Optical Properties in BiFeO3 Due to Different Exchange Interactions Between Transition and Rare Earth Ions
(John Wiley and Sons Inc, 2023) Seema Kumari; Khyati Anand; Mohd Alam; Labanya Ghosh; Srishti Dixit; Rahul Singh; Anil Kumar Jain; Seikh Mohammad Yusuf; Chetna Gautam; Anup K Ghosh; Anita Mohan; Sandip Chatterjee
An experimental analysis of the Bi0.90Tb0.1Fe0.90Mn0.1O3 system synthesized via the solid-state method is presented in this report. UV–visible measurements are carried out and a smaller bandgap (i.e., semiconductor-type behavior) is obtained. The structural phase of the present system is analyzed with X-ray diffraction and neutron diffraction measurement. Structural-phase analysis reveals that the system contains two nuclear phases (rhombohedral structure [R3c space group] with orthorhombic [Pn21a space group]). Moreover, also more bending in the bond angle is found, and the existence of a magnetic phase with a nuclear phase for the Bi0.90Tb0.1Fe0.90Mn0.1O3 system is also confirmed by neutron diffraction. The magnetic moment versus temperature (M–T) curve demonstrates that the system's Néel transition temperature is at 568 K. The magnetization data show enhancement in the magnetic property by displaying the weak ferromagnetic-type behavior at room temperature in the magnetic field versus magnetic moment (M–H) curve as compared to the parent compound. From dielectric measurement, the dielectric constant increases while the loss decreases. © 2023 Wiley-VCH GmbH.
Existence of exotic magnetic phases along with exchange bias and memory effect in frustrated beta-Mn Heusler alloy
(American Institute of Physics Inc., 2023) Srishti Dixit; Labanya Ghosh; Mohd Alam; Satya Vijay Kumar; Neha Patel; Swayangsiddha Ghosh; Nisha Shahi; Sanjay Singh; Sandip Chatterjee
Generally, Co-based Heusler alloys are the center of interest because of their properties such as high Curie temperature, spin polarization, and high value of exchange bias. Herein, we have used the macroscopic technique to probe the low-temperature exotic properties of M1.5Co0.5FeAl. First, we have analyzed the dc magnetization data, and it unfolds the presence of a glassy phase at 33 K. The cluster spin glass phase is authenticated by measuring ac susceptibility. Furthermore, using empirical models like power law and Vogel-Fulcher fitting, the relaxation time for the spin is of the order of τ ∼10-9 s, confirming the presence of a cluster spin glass in Mn1.5Co0.5FeAl below an irreversible temperature. The H-T phase space diagram ensures that it follows the Ising spin model. Furthermore, the glassy phase of the system is confirmed by magnetic relaxation, memory effect, and the presence of an exchange bias instead of a minor loop below spin-freezing temperature (TTf ~33 K). © 2023 Author(s).
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.
Giant dielectric constant, magnetocaloric effect and spin-phonon coupling in EuTbCoMnO6 semiconductor
(Elsevier B.V., 2023) Mohd Alam; Labanya Ghosh; Srishti Dixit; Madhusmita Jena; Seema Kumari; Satya Vijay Kumar; Dheeraj Kumar; Abhineet Verma; A.K. Ghosh; Satyen Saha; R.J. Choudhary; Sandip Chatterjee
Transport, dielectric, magnetic and Raman studies of polycrystalline double perovskite EuTbCoMnO6 have been performed. Temperature-dependent resistivity follows the variable range and small polaron hopping mechanism. The temperature-dependent dielectric study shows the usual frequency-dependent step-like behavior. It also shows thermally activated relaxor peak in loss curves with giant dielectric constant near room temperature. The temperature-dependent magnetization demonstrates a second-order phase transition around 113 K. The critical behavior near the magnetic transition has been systematically investigated. The Widom scaling relation and magnetic entropy change calculation have verified the reliability of critical parameters. Maximum magnetic entropy change around the magnetic transition temperature shows the magnetocaloric effect. The estimated values of critical parameters are close to the value of the theoretical mean-field model. Temperature-dependent Raman study shows spin-phonon coupling in the system. The appearance of the magnetocaloric effect and colossal dielectric constant shows that these materials are interesting for real-life applications. © 2023 Elsevier B.V.
Multifunctional behaviour in B-site disordered double perovskite EuPrCoMnO6
(IOP Publishing Ltd, 2022) Mohd Alam; Labanya Ghosh; Supriyo Majumder; Prajyoti Singh; Satya Vijay Kumar; Srishti Dixit; Dheeraj Kumar; Khyati Anand; Seema Kumari; A.K. Ghosh; R.J. Choudhary; Sandip Chatterjee
We report magnetic, transport, dielectric, and complex impedance of polycrystalline double perovskite EuPrCoMnO6 which crystallizes in disordered orthorhombic phase with space group Pnma. The DC magnetization shows two successive ferromagnetic transitions around 146 K and 138 K. The temperature and magnetic field variation of DC-susceptibility suggest the existence of Griffith phase and spontaneous exchange bias. AC susceptibility measurement shows a glassy dynamic behaviour near ferromagnetic transition. Further, a re-entrant glassy dynamic state is seen at a low temperature around 40 K. Temperature-dependent resistivity shows semiconducting/insulating nature, which gets increased under the application of magnetic field, showing positive magnetoresistance. The dielectric study shows usual frequency-dependent step-like behaviour with a colossal dielectric constant near room temperature. The complex impedance study shows both grain and grain boundary contribute to the electrical properties. The observed properties suggest the material can be used for spintronic devices and high dielectric applications. © 2022 IOP Publishing Ltd.
Multiple Magnetic Phases and Anomalous Hall Effect in Sb1.9Fe0.1Te2.85S0.15 Topological Insulators
(American Chemical Society, 2023) Debarati Pal; Abhineet Verma; Mohd Alam; Sambhab Dan; Amit Kumar; Seikh Mohammad Yusuf; Soma Banik; Sujay Chakravarty; Satyen Saha; Swapnil Patil; Sandip Chatterjee
Due to fundamental and technological concerns, investigating materials with topological magnetic structures has always been a focus of significant research. We explored Sb1.9Fe0.1Te2.85S0.15 where a unique combination of disordered glassy phases, competitive FM-AFM interactions, and nontrivial surface state coexisted at the same time. We have discussed the impact of those complicated magnetic phases upon the observed AHE in Sb1.9Fe0.1Te2.85S0.15 with magneto-transport studies. The AC susceptibility results demonstrate a shift in the freezing temperature with excitation frequency, the comprehensive analysis verifies the slower dynamics, and a nonzero Vogel-Fulcher temperature T0 suggests cluster spin glass. This, together with an intermediate value of the Mydosh parameter, provides an evidence for the formation of a cluster spin glass state in the present system. Topological frustrated magnets, which can host both magnetic frustrations and Dirac quasi-particles, are highly sought after class of compounds. Furthermore, as seen by the de Haas-van Alphen (dHvA) oscillation study, the fermiology deviates with doping and produces multiple Fermi pockets, revealing a rich complexity in the underlying electronic structure. © 2023 American Chemical Society.
Observation of the multiple magnetic phases in double perovskite Pr1.8La0.2CoFeO6
(Elsevier B.V., 2024) Dheeraj Kumar; Prajyoti Singh; Mohd Alam; Satya Vijay Kumar; Srishti Dixit; Krishanu Bandyopadhyay; G.D. Dwivedi; Satyen Saha; A.K. Ghosh; Sandip Chatterjee
The structural and magnetic properties of the double perovskite Pr1.8La0.2CoFeO6 have been investigated. The X-ray diffraction study shows that the system acquires room-temperature orthorhombic phase with the Pnma space group. The X-ray photoemission spectroscopy (XPS) measurement confirmed that the B-site ions are present in mixed valence states i.e. Co has been found in Co2+ and Co3+ valance states whereas Fe has been found in Fe3+/Fe4+. Magnetic measurements of the system confirm the existence of several fascinating magnetic behaviors, such as long-range canted antiferromagnetism withTN ∼ 271 K, giant exchange bias, and re-entrant cluster glass phase (TG ∼ 33 K). Field-dependent magnetization shows a large spontaneous exchange bias; HSEB∼ 1.8 kOe and giant conventional exchange bias, HCEB∼ 2.4 kOe at 5 K. Antiferromagnetic materials with large exchange bias can be utilized in high-density spintronic devices. Temperature-dependent Raman study demonstrates that the observed phonon mode exhibits anomalous behavior close to the magnetic transition temperature. Analysis of anomalous softening of phonon mode below TN, clarifies the presence of significant spin-phonon coupling while the magnetostriction effect does not play any significant role in the observed phonon anomaly. © 2024
Probing the Griffiths like phase, unconventional dual glassy states, giant exchange bias effects and its correlation with its electronic structure in Pr2-xSrxCoMnO6
(Institute of Physics Publishing, 2020) Arkadeb Pal; Prajyoti Singh; V.K. Gangwar; Amish G Joshi; P. Khuntia; G.D. Dwivedi; Prince K. Gupta; Mohd Alam; Khyati Anand; K. Sethupathi; Anup K. Ghosh; Sandip Chatterjee
Crystal, electronic structure, dc and ac magnetization properties of the hole substituted (Sr2+) and partially B-site disordered double perovskite Pr2-xSrxCoMnO6 system have been investigated. The XRD pattern analysis showed a systematic decrease in the lattice parameters owing to the enhanced oxidation states of the Co/Mn ions. The electronic structure study by XPS measurements suggested the presence of mixed valence states of the B-site ions (Co2+ /Co3+ and Mn3+ /Mn4+) with significant enhancement of the average oxidation states due to hole doping. The mere absence of electronic states near the Fermi level in the valence band (VB) spectra for both pure (x = 0.0) and Sr doped (x = 0.5) systems indicated the insulating nature of the samples. Sr substitution is observed to increase the spectral weight near the Fermi level suggesting for an enhanced conductivity of the hole doped system. The dc magnetization data divulged a Griffiths like phase above the long-range ordering temperature. A typical re-entrant spin glass like phase driven by the inherent anti-site disorder (ASD) has been recognized by ac susceptibility study for both the pure and doped systems. Most interestingly, the emergence of a new cluster glass like phase (immediately below the magnetic ordering temperature and above the spin-glass transition temperature) solely driven by the Sr substitution has been unravelled by ac magnetization dynamics study. Observation of these dual glassy states in a single system is scarce and hence placed the present system amongst the rare materials. The isothermal magnetization measurements further probed the exhibition of the giant exchange bias effect originated from the interfacial exchange interactions due to existence of low temperature antiferromagnetic clusters embedded in the glassy matrix. © 2020 IOP Publishing Ltd.
Raman effect and unusual transport properties of Co-doped Mn2FeAl Heusler alloy
(Institute of Physics, 2023) Srishti Dixit; Swayangsiddha Ghosh; Neha Patel; Mohd Alam; Krishanu Bandyopadhyay; Nisha Shahi; Yogendra Kumar; M. Sawada; K. Shimada; Satyen Saha; Sanjay Singh; Sandip Chatterjee
Semiconducting materials with a distinctive blend of high electrical and low thermal conductivity are required for efficient thermoelectric devices. In this aspect, Heusler alloys are potential candidates for thermoelectric materials. It has been observed that Co doping in Mn2FeAl enhances the electrical conductivity as well as reduces the thermal conductivity of the system leading to an improvement in figure of merit. The Seebeck coefficient suggested the p-type behavior over the whole temperature range, followed by a maximum at 150 K. Additionally, the electronic properties of the suggest that the observed Raman mode is due to the electronic excitations in the system. Interestingly, this system shows a decoupling between the Seebeck coefficient and electrical conductivity, suggesting the promising potential of as a thermoelectric material and offering valuable insights into its electronic properties. Copyright © 2024 EPLA.
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).
Spontaneous exchange bias and large dielectric constant in Bi0.8Tb0.2Fe0.8Mn0.2O3multiferroic
(American Institute of Physics Inc., 2022) Seema Kumari; Khyati Anand; Mohd Alam; Labanya Ghosh; Swayangsiddha Ghosh; Prince Gupta; Rahul Singh; A.K. Jain; S.M. Yusuf; Anup K. Ghosh; Anita Mohan; Sandip Chatterjee
The structural, dielectric, and magnetic properties of Bi0.8Tb0.2Fe0.8Mn0.2O3 have been studied in detail. A structural shift from rhombohedral (space group R3c) to orthorhombic (space group Pn21a + Pnma) phase is observed with doping. The substitution of Mn and Tb gives a very large value of the dielectric constant. It has been demonstrated that the observed spontaneous exchange bias is larger than the conventional exchange bias at room temperature. Moreover, doping reduces the Neel temperature from 643 to 521 K and magnetization increases. Thermoremanent magnetization studies at room temperature show that the system is composed of an interfacial layer of an antiferromagnetic core and a two-dimensional diluted antiferromagnet shell with a net magnetization under the field. Furthermore, the system's reasonable HEB and HC values at room temperature make it intriguing and appealing for a variety of multifunctional devices. © 2022 Author(s).
Study of spin-freezing transition in Pyrochlore Eu1.9Ce0.1Ti2O7 from ac-susceptibility measurement
(American Institute of Physics Inc., 2020) Mohd Alam; Arkadeb Pal; Prajyoti Singh; Surajit Ghosh; Sandip Chatterjee
In the present investigation, we report structural and magnetic properties of Ce doped (5% at the Eu site) Eu2Ti2O7 (ETO) pyrochlore. From the Rietveld analysis of the x-ray diffraction pattern, prepared samples were found to possess a single-phase cubic structure (Fd-3m). Curie-Weiss (CW) analysis and isothermal magnetization curve imply that anti-ferromagnetic interactions exist in the system AC susceptibility measurements confirm that there is almost no effect on spin freezing with such a small amount of Ce doping. © 2020 American Institute of Physics Inc.. All rights reserved.