Highly textured cobalt ferrite (CFO) thin films were grown on Si (100) substrates using oblique-angle pulsed laser deposition (α-PLD). X-ray diffraction and in-depth strain analysis showed that the obliquely deposited CFO films had both enhanced orientation in the (111) crystal direction as well as tunable compressive strains as a function of the film thicknesses, in contrast to the almost strain-free polycrystalline CFO films grown using normal-incidence PLD under the same conditions. Using in situ optical plume diagnostics the growth parameters in the α-PLD process were optimized to achieve smoother film surfaces with roughness values as low as 1-2 nm as compared to the typical values of 10-12 nm in the normal-incidence PLD grown films. Cross-sectional high resolution transmission electron microscope images revealed nanocolumnar growth of single-crystals of CFO along the (111) crystallographic plane at the film-substrate interface. Magnetic measurements showed larger coercive fields (∼10 times) with similar saturation magnetization in the α-PLD-grown CFO thin films as compared to those deposited using normal-incidence PLD. Such significantly enhanced magnetic coercivity observed in CFO thin films make them ideally suited for magnetic data storage applications. A growth mechanism based on the atomic shadowing effect and strain compression-relaxation mechanism was proposed for the obliquely grown CFO thin films.

Layered films of Pb(Zr 1-x Ti x )O 3 (PZT) and La x Sr 1−x MnO 3 (LSMO) are well-known multiferroic systems that show promise for numerous applications including data storage devices and spintronics. In this work, structure-property relationships are explored in novel PZT/CoFe 2 O 4 (CFO)/LSMO heterostructures with optimized ferroic properties. High quality, epitaxial PZT/CFO/LSMO heterostructures with the thickness of the CFO layer varying from 0 nm to 50 nm were grown on SrTiO 3 (100) substrates using an optimized pulsed laser deposition technique. An ultrathin (10 -20 nm) CFO layer was found to simultaneously improve the ferromagnetic and ferroelectric characteristics of the system through distinct mechanisms. The increase in magnetization and magnetic coercivity in the CFO-containing samples was associated with a tetragonal distortion of the CFO lattice under epitaxial strain, while perpendicular anisotropy generated by the distortion stabilized an out-of-plane orientation of the easy axis of magnetization in the thinnest CFO layers. Trapped charge at the CFO/PZT interface in PZT/CFO/LSMO induced an internal built-in field in the heterostructures, resulting in the accumulation of higher switched charges during voltage cycling and enhanced polarization in the samples over PZT/LSMO. An increase in electric coercivity was also observed in the CFOcontaining heterostructures, and is discussed in terms of a dielectric/FE layered capacitor model. Above a critical thickness, ~ 50 nm, the presence of a CFO layer has a negative effect on both magnetization and polarization in PZT/CFO/LSMO as compared to PZT/LSMO.

We report on the directed upright growth of ferroelectric (FE) Pb(Zr0.52Ti0.48)O3 (PZT) nanowire (NW) arrays with large aspect ratios of >60 using a Ti seed layer assisted hydrothermal process over large surface areas on ITO/glass substrates. In a two-step growth process, Ti seed layer of low surface roughness with a thickness of ~500 nm and grain size of ~100 nm was first deposited by radio frequency (RF) sputtering which was subsequently used as substrates for the growth of highly dense, single crystalline PZT NWs by controlled nucleation. The electron emission properties of the PZT NWs were investigated using the as-grown NWs as FE cathodes. A low turn-on field of ~3.4 V/μm was obtained from the NW arrays, which is impressively lower than that from other reported values. The results reported in this work give direction to the development of a facile growth technique for PZT NWs over large surfaces and also are of interest to the generation of high current electron beam from FE NW based cathodes for field emitter applications.

High quality polycrystalline and epitaxial PbZr0.52Ti0.48O3/La0.7Sr0.3MnO3 (PZT/LSMO) multiferroic thin films were deposited on single-crystal Si (100) and SrTiO3 (STO) (100) substrates using pulsed laser deposition (PLD) technique. The deposition conditions were optimized to overcome some of the challenges during the growth of stoichiometric PZT/LSMO thin films (with LSMO as the bottom layers). The major setback of the preferential evaporation of Pb during the ablation of PZT target, which leads to the growth of non-stoichiometric, Pb-deficient PZT thin films with poor ferroelectric properties, was investigated by studying the laser-target interaction sites and intensified charge-coupled detector (ICCD) imaging of the laser-ablated plumes. X-ray studies revealed that the PZT/LSMO heterostructures deposited under the optimum conditions were highly crystalline. Atomic force microscope images showed uniform grain growth with surface roughness values as low as 1.6 nm. In- and out-of-plane magnetization measurements showed saturation of 263–310 emu/cm3 and the corresponding absence or presence of magnetic anisotropy in the PZT/LSMO heterostructures on Si and STO substrates, respectively. LSMO/PZT/LSMO capacitors showed high remnant polarizations of 25–44 μC/cm2 at coercive fields of ∼30 kV/cm. A comparative study was performed on the strained epitaxial PZT/LSMO films on STO substrates and the un-strained polycrystalline PZT/LSMO films on Si substrates.

We have grown a 50 nm thick magnetic layer of cobalt ferrite (CFO) on two Co-based amorphous ribbons of compositions Co65Fe4Ni2Si15B14 (type I) and Co69Fe4Ni1Mo2B12Si12 (type II) by a pulsed laser deposition technique. A comparative study of the influence of this CFO layer on the giant magneto-impedance (GMI) effect and field sensitivity (η) of the ribbons is presented. Our results reveal that the presence of the CFO layer enhanced both the GMI ratio and the field sensitivity of the ribbons. Relative to the plain ribbons, the GMI ratio and field sensitivity of the CFO-coated ribbons increased by 97% and 42% for type I and by 34% and 50% for type II, respectively. The enhanced effects are attributed to the modifications on the ribbon surface and closure of magnetic flux paths due to the CFO layer.