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**93**

**1. Introduction**

**Chapter 5**

**Abstract**

Nanostructures

*and Ravinder Kumar Kotnala*

Ferromagnetism in Multiferroic

BaTiO3, Spinel MFe2O4 (M = Mn,

Co, Ni, Zn) Ferrite and DMS ZnO

Multiferroic magnetoelectric material has significance for new design nanoscale spintronic devices. In single-phase multiferroic BaTiO3, the magnetism occurs with doping of transition metals, TM ions, which has partially filled d-orbitals. Interestingly, the magnetic ordering is strongly related with oxygen vacancies, and thus, it is thought to be a source of ferromagnetism of TM:BaTiO3. The nanostructural MFe2O4 (M = Mn, Co, Ni, Cu, Zn, etc.) ferrite has an inverse spinel structure, for which M2+ ions in octahedral site and Fe3+ ions are equally distributed between tetrahedral and octahedral sites. These antiparallel sublattices (cations M2+ and Fe3+ occupy either tetrahedral or octahedral sites) are coupled with O2- ion due to superexchange interaction to form ferrimagnetic structure. Moreover, the future spintronic technologies using diluted magnetic semiconductors, DMS materials might have realized ferromagnetic origin. A simultaneous doping from TM and rare earth ions in ZnO nanoparticles could increase the antiferromagnetic ordering to achieve high-Tc ferromagnetism. The role of the oxygen vacancies as the dominant defects in doped ZnO that must

*Kuldeep Chand Verma, Ashish Sharma, Navdeep Goyal*

involve bound magnetic polarons as the origin of ferromagnetism.

**Keywords:** magnetically ordered material, oxygen vacancies, spin glass

Multiferroics are combining multiple order parameters, offer an exciting way of coupling phenomena such as electronic and magnetic order. However, because simultaneous electric and magnetic order is difficult to achieve, multiferroicsespecially those that function at or approaching room temperature-are extremely rare. For a crystal, when electrons are surrounded atomic nuclei to orient themselves in a same fashion then the crystal induces macroscopic ferromagnetism and electrical polarization. Since induction of ferromagnetism is essential in the technologies that involved sensors, computer hard drives, power generation, etc. Recently, the diluted magnetic semiconductors (DMSs) such as ZnO, SnO2, TiO2, etc. have generated potential in spintronics because DMS has the collective ordering that mediated via semiconductor charge carriers, as well as electron scattering
