Chapter 6 - Multi-Functionality of Spintronic Materials

Abstract

Multiferroics and diluted magnetic semiconductors (DMSs) might hold the future for the ultimate spintronic devices. In the present chapter, we review the spintronic multiferroic systems based on perovskite BaTiO3 (BTO) and DMS ZnO nanostructures. We also focus on the chemical routes that synthesized multiferroic and DMS nanostructures and thin films. We discuss, in particular, the mechanism to the existence of ferromagnetism and ferroelectricity in perovskite BTO and distortions of the lattice structure, and how this can promote magnetoelectric (ME) responses. We have discussed a comparative study that report multiferroicity in transition metal (TM) substituted BTO nanoparticles for which the TM ions influenced both nanosize and lattice distortion of TiO6 octahedra. The room-temperature magnetic behavior of multiferroic BTO is discussed with antiferromagnetic interactions, which is strengthened by changing the doping level from TM and rare earth (RE) ions. The multiferroicity and polarization of BTO depend upon the impurity ions, lattice distortion, nanostructures, lone-pair electrons, charge ordering, Dzyaloshinskii–Moriya interactions. The relative permittivity of BTO/NiFe2O4 composite is decreased with applied dc magnetic field that can induce negative magnetodielectric effect which is the combination of spin pair correlation of neighboring spins and the coupling constant. By reducing the clamping effect in multiferroic composite and thin films, ferroelectric domain modification and distinct magnetization change proportional to different interfacial area around the BTO phase transition, which may pave the way to introducing ME coupling at nanoscale. It has potential in high-density multistate memory devices. The defects-assisted ferromagnetism due to bound magnetic polarons in TM and RE ions into ZnO nanostructures has been investigated. It results into antiferromagnetic f–d transitions. Using density functional theory, we have shown the occupancy of RE and TM ions (replacing Zn atoms) in the wurtzite ZnO structure.