Research & Publications
Exploration of near room temperature magnetoelectric coupling in BaFe₁₀Sc₂O₁₉:KNbO₃ composite
Prathamesh Deshmukh, Srishti Kashyap, Swastika Mukherjee, Surbhi Gupta, Sudip Mukherjee
Journal of Physics and Chemistry of Solids (2024)
Highlights:
- Strain-mediated coupling of the magnetic-electric properties of the composite systems.
- Distinct non-disperse ferroelectric-like anomaly coinciding with magnetic transition.
- Noticeable negative magnetodielectric response with 5.4%@1 kHz near room temperature.
- Magnetoelectric coupling relies on flexomagnetoelectric response.
Abstract:
The consequential experimental endeavour has been undertaken to investigate and control the strain-mediated coupling of the magnetic and electric properties of the composite systems composed of Sc-doped BaFe₁₂O₁₉ and KNbO₃. A distinct non-disperse ferroelectric-like anomaly is observed Tweak ~ 265 K, which concomitantly coincides with the magnetic Tcone transition. The observation of external magnetic field dependence dielectric response shows a noticeable decrease in permittivity values, indicating a negative magnetodielectric response. The maximum intrinsic magnetodielectric response is seen in the vicinity of room temperature with the magnetodielectric ratio of 5.4% @ 1 kHz. The linearity of -Δɛ′(H)% vs. M² plot is phenomenologically described with the Ginzburg–Landau theory with the magnetoelectric coupling term γP²M². The magnetoelectric coupling relies on strain to induce crystal deformations (flexomagnetoelectric response) on either the ferroelectric phase through magnetostriction or in the magnetic phase through the converse piezoelectric effect. Strain-induced changes in the magnetic as well as dielectric properties of the composites lead to strong magnetoelectric coupling to throw more light exploring a potential candidate for room-temperature multiferroic materials.
View ArticleExploring the role of Cu¹⁺ in quasi-1D Cu₁₋ₓLiₓO (x = 0.025)
Prathamesh Deshmukh, Pradip Kumar Jana, Swastika Mukherjee, Srishti Kashyap, Manisha Venkatesh, Sudhindra Rayaprol, Sudip Mukherjee
Journal of Alloys and Compounds (2025)
Highlights:
- Influence of hole-doping on structural, magnetic, transport properties of CuO.
- XPS confirms the presence of Cu¹⁺ and Cu³⁺ in addition to Cu²⁺.
- Cu¹⁺ helps to maintain a high dielectric constant at low temperature.
- Lowering of commensurate and incommensurate transition temperatures observed.
- Near antiferromagnetic ordering, p-type to n-type transition observed.
Abstract:
The influences of hole-doping in cupric oxide leads to a localization of charge carriers, accompanied by changes in crystal structure, magnetic and transport properties. The crystallographic structure and phase purity of the properly sintered sample is characterized by temperature-dependent neutron diffraction (ND) measurements where the composition is found as Cu₀.₉₇₅Li₀.₀₂₅O (CLO). Interestingly, the formation of Cu¹⁺ and Cu³⁺ in addition to the Cu²⁺ was confirmed from the x-ray photoelectron spectroscopy (XPS) study in CLO system. Magnetization measurements show shifting in commensurate and incommensurate transition temperatures TN1 ~ 82 K and TN2 ~ 204 K respectively, highlighting the sensitive correlation between structural parameters and antiferromagnetically ordered quasi-1D spin arrangement. Temperature-dependent ordered magnetic moment (ground state) of Cu in CLO is calculated from ND data using a mean-field equation which coincides concomitantly with incommensurate antiferromagnetic transition TN2. Above and below the said antiferromagnetic ordering temperature, a changeover was concluded from p-type to n-type conduction mechanism. The Cu¹⁺ specimens in CLO maintain a high dielectric value (~10³) even at low temperature. The Cu¹⁺ and charge order domains significantly influence the intriguing transport behavior (hole-hopping between Cu²⁺ and Cu³⁺) of CLO, with their effects strongly dependent on the antiferromagnetically ordered spin structures.
View ArticleNegative capacitance and magnetodielectric effect in Cu₂O-CuO ceramics
Swastika Mukherjee, Srishti Kashyap, Prathamesh Deshmukh, Riya Roy, Souvik Chatterjee, Sudip Mukherjee
Ceramics International (2025)
Abstract:
The present experimental study reveals that the influence of the strong spin-charge-lattice correlation in Cu₂O-CuO ceramics leads to a localization of charge carriers, accompanied by changes in crystal structure, transport conduction, and magnetic transition. In the low-frequency region, existence of significant negative capacitance behavior, inductive loop and phase angle dependence (sign changes from positive to negative) concomitantly coincides, described by hopping mechanism of charge carriers between two Cu species (Cu²⁺ and Cu¹⁺). Further, in the high-frequency domain, coupling of holes (electrons) and spin are observed by dielectric anomaly near the incommensurate magnetic phase transition temperature (TN2 ~ 230 K). In addition, a distinct non-dispersive ferroelectric-like anomaly is observed around Tm ~ 320 K, where asymmetric charge-hopping introduces a large dipole moment via bridging oxygen with Cu2+−δ - O - Cu1+−δ. Finally, the external dc magnetic field (9 tesla) causes a sizable decrease of ɛ′ value ongoing approximately above 200 K along with disappearance of Tm ~ 320 K, representing the negative magneto-dielectric (MD) effect. This intriguing characteristic near the vicinity of magnetic transition can be established by the mechanism of charge-hopping-mediated MD effect, where the external applied field favors the double-exchange magnetic interaction by reducing the dipole moment and hence the dielectric permittivity value associated with the disappearance of the dielectric anomaly occurs.
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