arXiv subjects

Suchita Pandey

Publications and source records attributed to Suchita Pandey.

3 recordsLinked to original sources

arXiv2019

Harmonic Magneto-dielectric Study in Doped Perovskites, and Double Perovskite

Fundamental and harmonic magneto-dielectricity studied for varied perovskite systems-- Pb0.98Gd0.02(Mg1/3Nb2/3)0.995O3 (A-site co-doped PGMN magneto-relaxor), La0.95Ca0.05CoO3 (A-site doped spin-state LCCO), and La2NiMnO6 (double-perovskite LNMO multiglass) characterize intricately polarized phases. First-harmonic signal (ε2') of magnetically co-doped PGMN manifests finite polarization P(H) below 270K, corroborated by the measured remnant P-E traces. Second-harmonic (ε3') reveals the effect of random E-fields causing electrical vitreousity, latter indicated by the divergent timescale of the fundamental response. LCCO features mixed-dipoles phase over appreciable temperature window, affiliated to the coexistent low-spins (LS) and intermediate-spins (IS). Across the 65K-start of IS-to-LS state transition (SST), dc- and ac-conductivities of LCCO exhibit mechanism-changeovers whereas the harmonic susceptibilities evidence IS/LS-interfacial hyper-polarizations. Below the 30K-end of SST, harmonics corroborate the vitreous phase of dipoles in the LS-matrix state. In the LNMO, positive and negative (dual) magneto-dielectricity observed is respectively attributed to the charge-hopping between Ni2+ and Mn4+ ions and the interfacial polarization. Second-harmonic signal here also features dispersion corresponding to the activation energy required for the electron transfer between Ni- and Mn-cations. Results from three different perovskite systems signify the combined importance of first- and second-harmonics, for a detailed understanding of electrical configurations.

cond-mat.mtrl-sci↗

arXiv2017

Magneto-Dielectric Behavior in $La_{0.53}Ca_{0.47}MnO_{3}$

We prospect magneto-dielectricity in $La_{0.53}Ca_{0.47}MnO_{3}$ across its paramagnetic (PMI) to ferromagnetic (FMM) isostructural transition at $T_{C} \sim 253K$, by magnetic ($(M)$), caloric ($(W)$), dielectric ($(ε')$), magneto-resistive (MR), and magneto-capacitance (MC) investigations. Skew-broadened first-order transition character is confirmed via heating/cooling hystereses in $(M)(T)$ and $(W)(T)$, with superheating temperature $T**$ almost next to $T_C$ and supercooling temperature $T*$ exhibiting kinetics. Above $T_C$, linearly-related MC and MR reflect purely magneto-resistance effect. Near $T_C$, the high-frequency MC(5T) much exceeds the magneto-losses, and is uncorrelated with dc MR(5T) in the FM-ordered state. The intrinsic magneto-dielectricity manifest below $T_C$ and above ~kHz is traced to an intra-granular Maxwell-Wagner-type effect at the interface-region of PMI-FMM phase-coexistence.

cond-mat.mtrl-sci↗

arXiv2016

Magneto-thermally Activated Spin-state Transition in La0.95Ca0.05CoO3: Magnetically-tunable Dipolar Glass and Giant Magneto-electricity

Magneto-dielectric spectra of La0.95Ca0.05CoO3 covering the crossover of spin states reveals strong coupling of its spin and dipolar degrees of freedom. Signature of spin-state transition at 30K clearly manifests in magnetization, supported by Co L_3,2-edge XAS data on the doped-specimen as consistent with its suppressed T_SST vs. ~150K for pure LaCoO3. Dispersive activation-step Δε'(T_ω)~O(10^2) and relaxation-peak ε"(T_ω) reflect the allied influence of coexistent spin-states on the dielectric character. Dipolar relaxation in the LS regime below T_SST is partly segmental (VFT kinetics) featuring magnetic-field tunability, whereas in the LS/IS-spin disordered state above 30K, it is uncorrelated (Arrhenic kinetics) and almost impervious to the H-field. Kinetics-switchover defines the dipolar-glass transition temperature Tg(H), below which the magneto-thermally-activated cooperative relaxations freeze-out by the VFT temperature T_0(H). Applied H-field facilitates thermally-activated SST and accelerates the dipolar relaxations; a critical 5T field collapsing the entire kinetics into a single Arrhenic behavior. Magneto-electricity (ME) spanning sizable thermo-spectral range registers diverse signatures here in the kinetic, spectral, and field behaviors, in contrast to the static/perturbative ME observed close to the spin-ordering in typical multiferroics. Intrinsic magneto-dielectricity (50%) along with vanishing magneto-loss is obtained at (27K/50kHz)_9T. Sub-linear deviant field-hysteretic split seen in ε'(H)|_>4T suggests the emergence of robust dipoles organized into nano-clusters, realized by the internally-generated high magneto-electric field. An elaborate ω-T multi-dispersions diagram maps the rich variety of phase/response patterns, revealing the highly-interacting magnetic and electric moments in the system.

cond-mat.mtrl-sci↗