arXiv subjects

Pooja Sahlot

Publications and source records attributed to Pooja Sahlot.

5 recordsLinked to original sources

arXiv2020

Crystallite-size Dependent Harmonic Magneto-electricity in SmFeO3

First- and second-harmonic dielectric susceptibilities are maidenly studied on Samarium Orthoferrite of mesoscopic/500 nm and nanoscopic/55 nm grainsizes. Magneto-electrically coupled to the antiferromagnetic and spin-reorientation transitions, fundamental and harmonic dielectricity consistently reflect the global/local polarization effects of crystallite-size dependent electrical orderings. Bulk and incipient ferroelectricity respectively in nanoscopic and mesoscopic crystallites concur the higher-temperature antiferromagnetic ordering (T_N ~670 K). Upon the spin-reorientation transition at lower-temperature (T_SR ~470 K), re-entrant relaxor state in the nano-crystallites and bulk-like/temperature-windowed ferroelectricity in the meso-crystallites emerge. In the nano-crystallites, magneto-electric signature of interfacial spins' de-pinning (T_SP ~540 K) is exclusively revealed by the scaled-harmonics.

cond-mat.mtrl-sci↗

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↗

arXiv2019

Uncompensated-spins Induced Weak Ferromagnetism in Ca3Mn2O7: Magneto-conductive and dual Magneto-capacitive Effects

Temperature dependent magnetization study on single phase orthorhombic Ruddlesden-Popper manganite Ca3Mn2O7 evidences antiferromagnetic (AFM) ordering below 123K. Field-dependent magnetization M(H) depicts off-centered hysteretic loops below ~110K-- confirming the existence of both weak ferromagnetism (WFM) and exchange bias, whose development upon cooling is examined in detail. WFM is attributed to the formation of uncompensated-spin-clusters within the AFM-matrix, stabilized by the high-anisotropy in the manganite, favoring Dzyaloshinskii-Moriya (D-M) interaction. Temperature dependence of an evaluated average canting angle from the M(H) loops provides a quantitative measure of the WFM-evolution. Dielectric measurements exhibit magneto-conductive effects concurrent to the WFM-onset. Temperature dependence of the low-frequency/dc-limit of Jonscher-fits to the conductivity isotherms confirms the presence of relatively more-conductive clusters, embedded in the insulating-bulk. Nyquist impedance-analysis of complex impedance reveals two relaxations, yielding dual magnetic-field effects; the lumped circuit parameters feature anomalies across the magnetic phase changes.

cond-mat.mtrl-sci↗

arXiv2019

Spin-lattice Coupling and Magneto-dielectricity in Ca3Mn2O7 Layered Perovskite

Dielectric study on Ca3Mn2O7 features relaxor-like segmented dynamics below the antiferromagnetic ordering. Dipolar relaxations of different origin are spectrally resolved exhibiting distinct H-field alterations. This identifies their allegiance to different magnetic sub-phases and establishes dual coupling of electrical, magnetic, and structural degrees of freedom. Further, strong spin-lattice coupling has been affirmed with Raman spectroscopy across the magnetic ordering. Short-range electrical correlations collaterally cause measurable harmonic dielectric response in the system. The \c{hi}_3^e-susceptibility signal yields genuine harmonic magneto-dielectricity, consistent with but exhibiting two orders of magnitude larger H-field effect, vis-à-vis that obtained in the fundamental dielectric constant ε'.

cond-mat.mtrl-sci↗

arXiv2019

Interplay of Spin, Lattice, and Charge Degrees of Freedom in Ca3Mn2O7

From low-temperature Synchrotron X-ray diffraction, a precise thermal characterization of octahedral distortions in single phase Ruddlesden-Popper Ca3Mn2O7 is performed. Highly sensitive close-steps temperature dependences of Mn-O-Mn bond angles connecting MnO6 octahedra clearly reveal signature of the spin-ordering in the system. Spin-lattice coupling is thus established via the structural distortions responsible for evolution of the magnetic state. Further, temperature anomalies observed here in volume and polarization-measure of the unit cell highlight the interplay between spin, lattice and charge degrees of freedom. Dipole-relaxation characteristics examined under applied magnetic field consistently corroborate the concurrent magnetic and structural changes, in terms of genuine and intrinsic magneto-dielectricity.

cond-mat.mtrl-sci↗