Harmonic magneto-dielectric study in doped-, double-, and layered-perovskites

Abstract

Harmonic magneto-dielectricity studied for the perovskite systems—Pb0.98Gd0.02(Mg1/3Nb2/3)0.995O3 (PGMN), La0.95Ca0.05CoO3 (LCCO), La2NiMnO6 (LNMO), and Ca3Mn2O7 (CMO), precisely characterizes intricately polarized phases. In magnetically co-doped PGMN, the first-harmonic signal (χ2′) manifests finite polarization P(H) below 270 K, corroborated by the measured remnant P–E traces. The second harmonic (χ3′) reveals the effect of random E-fields, causing electrical vitreousity. In spin-state LCCO, across the 65K-start of intermediate- (IS) to low-spin (LS) transition, harmonic susceptibilities evidence IS/LS-interfacial hyper-polarizations, and ac-/dc- conductivities exhibit mechanism-changeovers. In charge-transfer LNMO, dual magneto-electricity due to Ni2+ ↔ Mn4+ charge-hopping (intrinsic) and Maxwell–Wagner (fictitious) polarizations gets distinguished via χ2′. In hybrid improper ferroelectric (HIF) CMO, while the χ2,3′-signals clearly evidence stabilization of the ferroelectric state below 50 K, χ3′ and ɛ* discern the super-paraelectric, coupled-relaxor, and glassy phases, magneto-electrically coexistent with short-range spin-correlations, antiferromagnetic, and weak-ferromagnetic states, respectively. Our results on a variety of perovskites establish harmonics' exclusivity in revealing novel phases and superiority in divulging subtly variant states, either escaping detection or rendered indescript by usual electrical characterizations.