Investigation of magnetoelectric coupling in (1-x)Ba0.95D0.05TiO3 + xLi0.1Cu0.1Co0.1Zn0.6Fe2.1O4 (D = Sr, Ca) multiferroics for novel memory devices

Abstract

Various (1-x)Ba0.95D0.05TiO3 + xLi0.1Cu0.1Co0.1Zn0.6Fe2.1O4 composites (where, D = Sr, Ca; x=0.0, 0.1, 0.2, 0.3, 0.4, 0.8, and 1.0 ) were synthesized and studied in detail. The X-ray diffraction patterns of Ba0.95D0.05TiO3 (BSTO/BCTO) confirm the perovskite structure with P4mm space group, and Li0.1Cu0.1Co0.1Zn0.6Fe2.1O4 (LCCZFO) confirm t he c ubic s pinel s tructure w ith F d-3m s pace g roup. I n the composites, both phases are co-existed without any third phase. The lattice parameters are found almost constant, and density is found to decrease with LCCZFO content. The Field Emission Scanning Electron Microscopy images confirm that the grain distributions are homogeneous and the average grain size increased with the increasing LCCZFO content in the composites. The dielectric constant for both series of composites remains almost constant throughout the studied frequency range. The temperature-dependent dielectric constant exhibits ferroelectric to para-electric transition peaks at 423 K for both composite series. In impedance spectra analysis, the non-Debye type dipole relaxations have been found. At the same time, the grain boundary resistance was also found to decrease with increasing LCCZFO content in the Nyquist plots both for BSTO and BCTO series. The linearity in the log(σAC) versus log(ω) plot (20Hz-120MHz) indicates that conduction is mainly due to small polaron hopping. The real part of initial permeability and saturation magnetization increases with increasing LCCZFO content. The ferroelectric behaviour is observed for the composites up to x = 0.40. The magnetoelectric voltage coefficient (αME) increases with increasing LCCZFO content up to x= 0.15 and then decreased for further increasing of x. The maximum αME is found (287 mVcm−1Oe−1) for 0.85 Ba0.95Ca0.05TiO3 + 0.15 Li0.1Cu0.1Co0.1Zn0.6Fe2.1O4 composite. It is found that for some of the composites, both ferromagnetic and ferroelectric hysteresis loops exist at room temperature. Therefore, it can be concluded that the composites have a multiferroic nature. The present study may be helpful to design multi-functional hetero-structured read/write memory, switching and sensing devices.