Low Temperature Stabilization of Nanoscale Epitaxial Spinel Ferrite Thin Films by Atomic Layer Deposition

Abstract

In this work heteroepitaxial stabilization with nanoscale control of the magnetic Co2FeO4 phase at 250 °C is reported. Ultrasmooth and pure Co2FeO4 thin films (5–25 nm) with no phase segregation are obtained on perovskite SrTiO3 single crystal (100) and (110) oriented substrates by atomic layer deposition (ALD). High resolution structural and chemical analyses confirm the formation of the Co‐rich spinel metastable phase. The magneto‐crystalline anisotropy of the Co2FeO4 phase is not modified by stress anisotropy because the films are fully relaxed. Additionally, high coervice fields, 15 kOe, and high saturation of magnetization, 3.3 μB per formula unit (at 10 K), are preserved down to 10 nm. Therefore, the properties of the ALD‐Co2FeO4 films offer many possibilities for future applications in sensors, actuators, microelectronics, and spintronics. In addition, these results are promising for the use of ALD compared to the existing thin‐film deposition techniques to stabilize epitaxial multicomponent materials with nanoscale control on a wide variety of substrates for which the processing temperature is a major drawback.

Nanocrystalline Ferroelectric BiFeO3 Thin Films by Low-Temperature Atomic Layer Deposition

“…52,53 4 as 300ºC. 33,34 The surface of the as-grown layer is amorphous, which is in agreement with the RHEED results. In contrast, an annealing converts it into a fully crystalline layer.…”

“…[30][31][32] Most as-deposited ALD films are amorphous or polycrystalline, although epitaxial oxides can also be obtained in the as-deposited stage (< 300ºC) using structurally compatible buffer layers and single crystal substrates. [33][34][35][36] Among the ferroelectric perovskites, BiFeO 3 (BFO) is a stable, lead-free material that simultaneously presents ferroelectric and magnetic order at room temperature. 9,[37][38][39] In the literature, resistive-switching and photovoltaic responses have also been reported.…”

Atomically Flat Ultrathin Cobalt Ferrite Islands

“…Future advances in nanotechnology rely in part on our ability to accurately engineer high quality oxide‐based epitaxial nanostructures with customizable functionalities . However, control of properties at the nanoscale remains a challenge due to the critical influence of structural defects that proliferate at the ultrathin level, such as surface roughness or antiphase boundaries .…”

Synthesis and excellent electromagnetic absorbing properties of copolymer (N-methylpyrrole-co-pyrrole) and Ba–Nd–Cr ferrite

“…Compared with the dielectric loss media, the magnetic loss media can be fabricated into the thin high-efficient EMW absorbents because of the high magnetic loss [7,8], among which the ferrite is an excellent EMW absorbent due to the advantages of the high permeability, strong magnetism, and easy preparation. Recently, several types of ferrites have been reported, such as spinel ferrite [9,10], Z-type [11,12], W-type [13,14], Y-type [15] and M-type magnetoplumbite [16,17]. Ba ferrite, among them, has been widely studied due to its strong magnetism and high electrical resistivity in the range of 10 6 -10 9 Hz [14,18,19].…”