Effect of Underlayer Quality on Microstructure, Stoichiometry, and Magnetic Properties of Hexaferrite BaFe₁₂O₁₉ Grown on YSZ(111) by Pulsed Laser Deposition

Abstract

We have studied the effect of platinum underlayer for two deposited thicknesses on the microstructure, crystalline quality, morphology, chemical composition, and magnetic properties as well as magnetic domain formation of BaFe12O19 (BaM) grown on YSZ(111) by pulsed laser deposition (PLD). We found that PLD platinum deposited with a thickness of 25 nm cannot withstand the dewetting phenomenon occurring during the subsequent BaM layer growth. A smooth and continuous Pt underlayer that possesses a sharp interface and omits the intermixing between the BaM and substrate was successfully achieved for a deposited Pt film thickness of 75 nm. Independent of the thickness of the deposited Pt layer, the c-axis orientation as well as coercivity Hc and the anisotropy H A fields were significantly improved due to a remarkable improvement of lattice mismatch in comparison with the BaM layer grown without a Pt underlayer on YSZ(111). By applying high-resolution X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), and atomically resolved scanning TEM imaging combined with energy-dispersive X-ray spectroscopy, as well as atomic and magnetic force microscopy, a comprehensive investigation of both structure and chemical composition of the deposited BaM films and their interfacial regions was performed. This study aimed to correlate the enhancement of the overall magnetic properties and of the local spin magnetic domain orientation with the modification of BaM microstructure and chemical composition at the nanometer scale due to the Pt underlayer. Finally, we attempted to understand the mechanisms that control the magnetic properties of these BaM films in order to be able to tailor them.

Dependence of the Structural and Magnetic Properties on the Growth Sequence in Heterostructures Designed by YbFeO3 and BaFe12O19

“…It has covered thin-film heterostructures such as SrBa 2 Ta 2 O 9 /BaM [ 1 , 2 ], Ba 2 EuFeNb 4 O 15 /BaM [ 3 , 4 ], multilayers composed of BaM layers with Pb(Zr,Ti)O 3 (PZT) [ 5 ] or (Ba,Sr)TiO 3 (BST) [ 6 , 7 , 8 ] or BaTiO 3 perovskite layers [ 9 ], and multiferroic composites [ 10 , 11 , 12 ]. BaM is a very attractive material due to the high anisotropy H a and coercivity H C fields [ 13 , 14 ], which are beneficial for obtaining performant film in perpendicular recording media. h-YbFeO 3 belongs to the hexagonal rare earth ferrites h-(RFeO 3 ) with R = Dy, where ferroelectricity and antiferromagnetism have been demonstrated at low temperatures [ 15 ].…”

Relevance of Platinum Underlayer Crystal Quality for the Microstructure and Magnetic Properties of the Heterostructures YbFeO3/Pt/YSZ(111)

“…In our opinion, there is a lack of deep understanding about the dependence of the h-YbFO 3 microstructure on the growth parameters and particularly on the quality of the underlayer between the YbFeO 3 film and the used substrate. Recently, Bauer et al [ 15 ] demonstrated the relevance of the Pt underlayer quality for the crystal structure as well as the magnetic properties of hexaferrite BaFe 12 O 19 films. They proved that PLD growth of an optimum platinum underlayer thickness significantly enhances the layer quality and the magnetic performance of the ferromagnetic layer.…”