Carrier-mediated ferromagnetism and dielectric tailoring in dual-doped ZnO semiconductor nanoparticles for spintronics

Abstract

The research and development of modified nanomaterials is critical for spin-based electronics storage systems, particularly novel magnetic materials with 100 % spin polarization at room temperature. This feature is present in a number of Zintl group compounds and should be investigated. This work thoroughly investigated the impact of (Co, Eu) co-doping on the structural, electrical, dielectric, and ferromagnetic properties of ZnO nanoparticles. At all doping concentrations, the tetragonal phase was retained, according to X-ray diffraction (XRD) examination. Dielectric investigations showed that while the dielectric constant (ε_r') and dielectric loss (ε'') decreased with increasing Eu content, the frequency-dependent improvement of AC electrical conductivity (σ_AC) was ascribed to charge hopping among nanograins and dielectric relaxation impacts. Magnetic studies were presented to explore the ferromagnetic response further, revealing a shift from diamagnetic behavior in pure ZnO to robust room-temperature ferromagnetism (RTFM) in Co-doped and (Co, Eu) co-doped ZnO nanoparticles. Strong carrier-mediated exchange contacts and defect-induced magnetism were shown by the increased remanent magnetization (Mr) and coercivity (Hc) that accompanied increasing Eu content, peaking at 5 % Eu doping. Ferromagnetic ordering with a Curie temperature (T_C) of roughly 370 K for optimally doped materials was validated by Arrott plot analysis. The exchange interactions, defect-induced effects, and structural deformation all contribute to the magnetism in ZnO caused by Co and Eu doping. While Eu³⁺ participates by forming partially filled 4f orbitals, Cobalt (Co²⁺) ions contribute localized magnetic moments because of unpaired 3d electrons when they substitute Zn²⁺ in the ZnO lattice. These dopants interaction facilitates long-range ferromagnetic coupling via carrier-mediated exchange processes, which include bound magnetic polarons (BMPs), in which oxygen vacancies trap charge carriers. The findings show that co-doped ZnO ferromagnetic behavior may be efficiently modulated by controlled Eu co-doping, which makes these materials attractive options for spintronic applications.