Correlation between Magnetoelectric Coupling and Grain Size of a Magnetoelectric Particulate Composite System

Abstract

Today’s advanced growing technological era, global scientific as well as commercial communities are given special interest in multifunctional magnetoelectric (ME) composites due to induce of significant coupling between ferroelectric (FE) and magnetic ordering even in low field and high temperature (which is absent in single phase ME systems) 1 . So these systems can be superior than single phase towards various applications: spintronic, solid-state transformers, high sensitivity magnetic field sensors and miniature antennas, etc 2,3 . It has been found that, in a ME composite system ME coupling (MEC) is a strain meditated which is induced at the interface of piezoelectric/ferroelctric and pizzomagnetic phases1. In 1972 Van Suchtelen has been proposed that, the MEC in these systems is4 :𝜕𝑃𝜕𝐻 = 𝛼 = 𝑘𝑐𝑒𝑚𝑒, where 𝑘𝑐 is a coupling factor and 𝛼 is the ME coefficient, where 𝑒 and 𝑒𝑚 are piezomagnetic and piezoelectric coefficients of the composite system. So to achieve better ME coupling, high piezomagnetic and piezoelectric coefficients is necessary. Recently, we have been observed, MEC can be tailored with variation of grain size of both the phases in a two phase composite. The experiments have been carried out by considering 90 wt% Na0.5Bi0.5TiO3 (NBT) - 10 wt% BaFe12O19 (BaM) novel composite system [NBT(Lg) - BaM(Lg)], NBT(Lg) - BaM(Sg)], NBT(Sg) - BaM(Lg) and NBT(Sg) - BaM(Sg), where, Lg and Sg are assigned as larger and smaller grain respectively]. From analysis it has been perceived that, NBT(Sg) - BaM(Lg) has shown highest MEC than others. In summary, we have proposed a modified Van Suchtelen equation i.e. 𝜕𝑃 𝜕𝐻 = 𝛼 = 𝑘𝑐𝑒 𝑚𝑒 [(∑ 𝐹𝐸𝑔) ( 𝐺𝐹𝑀 𝐺𝐹𝐸 )], where ∑ 𝐹𝐸𝑔 - are the numbers of ferroelectric (FE) grains are connected with ferromagnetic (FM) phase and 𝐺𝐹𝑀 𝐺𝐹𝐸 is the ratio between the average grain size of FM to FE phase5 .