Browsing by Author "Seema Kumari"

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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.
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.
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
Spin phonon coupling and magneto-dielectric coupling in BiFeO3-TbMnO3 composite
(Institute of Physics Publishing, 2019) Prince K. Gupta; Surajit Ghosh; Seema Kumari; Arkadeb Pal; Somnath Roy; Rahul Singh; Prajyoti Singh; Ranjan K. Singh; A.K. Ghosh; Sandip Chatterjee
Magneto-structural and magneto-electric coupling in multiferroic composite BiFeO3-TbMnO3 have been investigated. Anomalous softening of the phonon modes was observed ∼210 K (close to the spin reorientation transition temperature T∗) in the temperature dependent Raman spectra which might be a result of spin phonon coupling in the lattice. Relaxor type ferroelectric behaviour was observed in the temperature dependent dielectric measurements where the relaxation was found near T∗. The frequency dependent dielectric study and the impedance spectroscopy revealed that the dielectric properties are a mixture of intrinsic Debye relaxation and Maxwell-Wagner relaxation arising from the space charge polarization at the interface of the composite. A large positive magneto-dielectric (MD) coupling was found near the relaxation temperature which is understood to be originated as a result of the magneto-structural coupling in the system. © 2019 IOP Publishing Ltd.
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).