Browsing by Author "Arkadeb Pal"

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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).
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.
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
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.
Hidden transition in multiferroic and magnetodielectric CuCrO2 evidenced by ac-susceptibility
(Institute of Physics Publishing, 2017) Kaushak K. Shukla; Arkadeb Pal; Abhishek Singh; Rahul Singh; J. Saha; A.K. Sinha; A.K. Ghosh; S. Patnaik; A.M. Awasthi; Sandip Chatterjee
Ferroelectric polarization, magnetic-field dependence of the dielectric constant and ac and dc magnetizations of frustrated CuCrO2 have been measured. A new spin freezing transition below 32 K is observed which is thermally driven. The nature of the spin freezing is to be a single-ion process. Dilution by the replacements of Cr ions by magnetic Mn ions showed suppression of the spin freezing transition suggesting it to be fundamentally a single-ion freezing process. The observed freezing, which is seemingly associated to geometrical spin frustration, represents a novel form of magnetic glassy behavior. © CopyrightEPLA, 2017.
High temperature spin-freezing transition in pyrochlore Eu2Ti2O7: A new observation from ac-susceptibility
(Elsevier B.V., 2018) Arkadeb Pal; Abhishek Singh; A.K. Ghosh; Sandip Chatterjee
The magnetization (both dc and ac) of pyrochlore Eu2Ti2O7 have been investigated. Ac susceptibility (χ/ & χ//) measurements reveal a new unusual spin freezing below 35 K for pure Eu2Ti2O7. Frequency dependence of these ac χ// peak positions indicate slow spin relaxation near this temperature and it follows the Arrhenius formula suggesting a thermally activated relaxation process. The origin of this spin freezing has been attributed essentially to a single ion process which is associated to Eu3+ spin relaxation. Non-magnetic dilution by Y3+ ions also confirms the single ion freezing. © 2018 Elsevier B.V.
Insights into local atomic structure of Fe alloyed ZnS nano crystals: Correlation with structural, optical, magnetic and photocatalyst properties
(Elsevier Ltd, 2019) Soumendra Ghorai; Nirmalendu Patra; Arkadeb Pal; Dibyendu Bhattacharyya; Shambhu Nath Jha; Biswajit Ray; Sandip Chatterjee; Anup K. Ghosh
The effect of Fe dopant on the structural, optical, magnetic properties and local atomic structure of aqueous synthesis derived Zn1-xFexS (0 ≤ x ≤ 0.06) nanocrystals have systematically investigated. The crystallite structure and crystallite size have been estimated by X-ray diffraction with Rietveld refinement and transmission electron microscopy. Scanning electron microscopy demonstrates the sphalerite morphology. Raman spectroscopy has been employed to observe the effect in crystalline quality and local defects on the host lattice. Defect formation due to Fe dopant on ZnS nanocrystals has been demonstrated by photoluminescence spectroscopy. The local electronic structure of Zn and Fe sites are investigated thoroughly by synchrotron based X-ray absorption spectroscopy. Significant fraction of Fe–Fe data of extended X-ray absorption fine structure suggests that interstitial Fe sites are present. The sphalerite ZnS and Fe doped ZnS (x = 0, 0.02 and 0.06) showed the photocatalytic activity in methylene blue solution at ambient pressure and temperature on visible and ultraviolet light irradiation. The results illustrate that higher Fe doped ZnS (x = 0.06) photocatalyst with sphalerite morphology has strong photocatalytic activity on ultraviolet irradiation. The temperature dependence magnetization of higher doping concentration (x = 0.06) has been explained with a combined model of spin wave and Curie Weiss fitting. The ferromagnetism at low temperature has been studied with bound magnetic polaron model. © 2019
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.
Observation of structural change-driven Griffiths to non-Griffiths-like phase transformation in Pr2-xSrxCoFeO6 (x = 0 to 1)
(Elsevier B.V., 2022) Arkadeb Pal; Khyati Anand; Dheeraj Kumar; Amish G. Joshi; Peter Tsung-Wen Yen; Shin-Ming Huang; H.D. Yang; A.K. Ghosh; Sandip Chatterjee
The study of crystal structure, electronic structure, transport, and magnetic properties of heterovalent Sr2+ doped Pr2-xSrxCoFeO6 (x = 0.0 to 1.0) system have been done. Crystal structure study reveals an occurrence of structural change from orthorhombic (Pnma) to tetragonal (I4/m) phase above x = 0.6. A sudden transformation of the Griffiths-like to non-Griffiths-like magnetic phase is observed as the system changes its crystal structure from Pnma to I4/m. The X-ray photoemission spectroscopy (XPS) study suggests for the existence of mixed oxidation states of the B-site ions viz., Co3+/Co4+ and Fe3+/Fe4+, and it also indicates an increase in the mean oxidation states owing to the hole substitution (Sr2+). The temperature variation of the electrical resistivity of the studied systems follows two different transport mechanisms, such as the variable range hopping (VRH) (in the lower temperature region) and small polaron hoping (SPH) (in the higher temperature region) models. Dc magnetization study shows that a local competing ferromagnetic (FM) exchange interaction increases with Sr doping. Finally, the ac susceptibility study reveals breaking of the long-range-ordering in the system x = 1.0, which appears to be related to the structural change and enhanced spin frustration due to increased competing local FM exchange interactions. In addition, electronic density of states (DOS) calculations of PrSrCoFeO6 (i.e. x = 1.0) using the density functional theory (DFT) have been performed for various Co/Fe atomic distributions. For most of the Co/Fe atomic distributions studied, the calculations show that the total energy of the system with FM coupling among spins has slightly lower energy than that for antiferromagnetic (AFM) coupling. © 2022
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.
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
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).
Spin freezing and field induced transition in (Tb1−xEux)2Ti2O7: A magnetic property study
(Elsevier B.V., 2019) Prajyoti Singh; Arkadeb Pal; Vinod K. Gangwar; Surajit Ghosh; Ranjan K. Singh; A.K. Ghosh; Sandip Chatterjee
The magnetic properties and Raman effect of (Tb1−xEux)2Ti2O7 have been investigated. Raman study indicates the existence of hardening due to phonon-phonon anharmonic interaction. The DC magnetic study indicates the significant contribution of dipolar and exchange interactions in Eu rich samples. From AC magnetic measurement, a partial single ion spin freezing around Tf = 33 K at zero magnetic field is observed in (Tb1−xEux)2Ti2O7. On applying a field of 10 kOe, all compounds show a field induced transition which shifts towards higher temperature with increase Eu content. This field induced transition might be attributed to the single moment saturation. © 2019 Elsevier B.V.
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.
Study of band structure, transport and magnetic properties of BiFeO3–TbMnO3 composite
(Springer Nature, 2019) Prince K. Gupta; Surajit Ghosh; Arkadeb Pal; Somnath Roy; Amish G. Joshi; A.K. Ghosh; Sandip Chatterjee
Charge transfer across the interface of two materials in a composite can create reconstruction of bands near the interface which in turn brings multiple changes in physical properties of the materials. Thus, investigation of band structure experimentally is of immense importance in studying composite materials to understand their physical properties. Here, we have studied magnetoelectric multiferroic composite of two types of multiferroic (types I and II) consisting of BiFeO3 and TbMnO3 for enhanced magnetic and transport properties. The band structure was investigated with the help of UV–visible absorption spectrum, the valence band X-ray photoemission spectra (XPS), and ultraviolet photoemission spectra. The band structure thus obtained can successfully explain the magnetic and transport properties of the composite. The insulating behavior of the system is understood from the reconstruction of the energy bands at the interface and subsequent decrease in the band gap which happens due to lattice mismatch of the two materials. The large coercivity and the increase in the magnetization value are understood to be due to superexchange interaction between different Mn ions (Mn2+, Mn3+, and Mn4+). From the composition study of EDXA and core-level XPS, oxygen vacancy was found which in turn creates the mixed valence state of Mn to maintain the charge neutrality. © 2019, Springer Nature Switzerland AG.
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.
Transport and dielectric properties of double perovskite Pr2CoFeO6
(American Institute of Physics Inc., 2018) Arkadeb Pal; A. Singh; V.K. Gangwar; Sandip Chatterjee
The transport and dielectric measurements have been investigated for the polycrystalline double perovskite Pr2CoFeO6. In the temperature dependent resistivity measurement, we have observed semiconducting nature of the sample with activation energy 0.246 eV. In dielectric measurement as a function of temperature, a giant value of dielectric constant is observed at room temperature, the frequency dependence suggests a relaxor type dielectric relaxation. © 2018 Author(s).