Texture and Magnetocrystalline Anisotropy in NiFe2O 4 Thin films Deposited via Chemical Solution Deposition

Spinel nickel ferrite with the chemical formula Fe3+[Ni 2+Fe3+]O4 (NFO) has attracted highly attentions for many applications due to its room temperature magnetic behavior, moderate electrical resistivity and, high Curie temperature. Along with other magnetic spinel cubic ferrites including CoFe2O4 and MnFe 2O4, NFO has long been considered as the magnetostrictive phase to fabricate magnetoelectric (ME) composites. One of the approaches to improve the ME response of the composites is to enhance the magnetostriction of the magnetic phase by texturing along its magnetic easy axis direction.;In this work, spinel cubic NiFe2O4 (NFO) thin films are derived via chemical solution deposition (CSD) technique. The films grown on Si substrates show a granular microstructure and surface roughness of 3 nm. The effects of varying the processing condition including pyrolysis and annealing temperature have been studied on the microstructure and the resulting magnetic properties. Microstructural studies confirm the formation of randomly oriented, phase-pure spinel nickel ferrite on Si substrates. It is shown that the pyrolysis temperature does not affect the microstructure and resulting magnetic properties, while increased the grain size as a results of increased annealing temperature influences the magnetic properties.;Magnetoelectric thin film multilayers are prepared also using NFO as the magnetostrictive phase and PbZr0.52Ti0.48O 3 (PZT) as the piezoelectric phase via CSD. The PZT/NFO composite microstructures are investigated through TEM and SEM studies and the interface is engineered to minimize the elemental interdiffusion between phases and the substrate. The dielectric property of the piezoelectric phase and the magnetic response of the magnetic phase are investigated. The addition of a Pt intermediate layer resulted in an improved dielectric properties obtained in Si/NFO/Pt/PZT composite configuration.;To improve the magnetostriction response of the NFO layer, same CSD method is employed to grow highly textured NFO thin films on Si/SiO2/TiO x/Pt and Al2O3 (0001) substrates. The deposited NFO thin films on Si/SiO2/TiOx/Pt substrates show complete uniaxial out-of-plane texture in the direction with random in-plane orientation. While X-ray ϕ-scanning indicates the out-of-plane texture as well as in-plane epitaxial relationships in two crystallographic variants between the films and the Al2O3 (0001) substrates. As the NFO magnetic easy-axis is , the out-of-plane magnetization for both textured thin films exhibits improved Mr/Ms (remanent) ratios with respect to the randomly oriented NFO films on Si substrates. However, compared to the uniaxially textured NFO films on platinized silicon, the films on the Al2O3 (0001) substrates show 10% increase in out-of-plane remanent ratio and 20% reduction in coercivity. In addition, both textured NFO thin films show enhanced magnetostrictive response compared to the randomly oriented films on the Si substrates. The improved out-of-plane magnetic anisotropy in the textured films is comparable to epitaxial NFO films of similar thickness deposited by pulsed laser deposition and sputtering Microstructural studies show that texturing initiates by nucleation of (111) planes at the film/substrate interface and decreases as the film thickness decreases.