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Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate.

Magnetization dynamics driven by an electric field could provide long-term benefits to information technologies because of its ultralow power consumption. Meanwhile, the Dzyaloshinskii-Moriya interaction in interfacially asymmetric multilayers consisting of ferromagnetic and heavy-metal layers can stabilize topological spin textures, such as chiral domain walls, skyrmions, and skyrmion bubbles. These topological spin textures can be controlled by an electric field, and hold promise for building advanced spintronic devices.Here, we present an experimental and numerical study on the electric field-induced creation and directional motion of topological spin textures in magnetic multilayer films and racetracks with thickness gradient and interfacial Dzyaloshinskii-Moriya interaction at room temperature. We find that the electric field-induced directional motion of chiral domain wall is accompanied with the creation of skyrmion bubbles at certain conditions.We also demonstrate that the electric field variation can induce motion of skyrmion bubbles.Our findings may provide opportunities for developing skyrmion-based devices with ultralow power consumption.The electric field (EF) induced spintronic phenomena could offer great benefits to the information-related industries, since they can be harnessed for building information processing devices with ultralow power consumption 1, 2 . Especially, the modification of magnetic parameters, such as the magnetic anisotropy 3-7 , plays an essential role in realizing magnetization switching 5, 8-12 , domain structure modification [13][14][15] , and domain wall motion [16][17][18][19][20][21] . Additionally, recent experiments on magnetic asymmetric multilayers show that the antisymmetric Dzyaloshinskii-Moriya interaction (DMI), which can be induced at the ferromagnet/heavy metal interface [22][23][24][25][26] , is able to further stabilize novel topological spin textures including chiral domain walls, skyrmions, and skyrmion bubbles. In a general context, the skyrmion bubble stands for the topologically non-trivial bubble with a fixed chirality but a larger size in compared with the compact skyrmion 24-26 . These topological spin textures also provide emerging opportunities for developing low-power information processing as well as high-density storage and logic computing technologies 22-29 , which have been theoretically predicted and experimentally demonstrated in the last decade [22][23][24][25]27 .

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Single crystal or textured growth with preferred orientation of transition-metal oxide thin films is highly desirable for their application in technological devices. Commercially available singlecrystal substrates are the obvious base to deposit thin films with a desired orientation. However, these substrates have inherent shortcomings including limited number of crystal structures, lattice parameters and orientations, and most importantly their high costs. Herein, a universal approach was developed to grow an oxide thin film with (100) crystal orientation on an amorphous substrate. To achieve this goal, two layers of the same material called self-bilayer were deposited at different temperatures and of different thicknesses. CoFe 2 O 4 spinel ferrite was used as a model system to realize the approach since it is difficult to grow spinel ferrites with (100) orientation even on single-crystal substrates. X-ray diffraction pattern and transmission electron microscopy confirmed the single-crystal-like growth of CoFe 2 O 4 with (100) orientation on an amorphous SiO 2 /Si substrate. The deposited CoFe 2 O 4 bilayer thin film displays unprecedentedly giant perpendicular magnetic anisotropy with a coercivity of 14.1 kOe, saturation magnetization of 475 emu/cm 3 , and remanent ratio of 0.92 at room temperature. This work opens up a facile and generic route to grow complex metal oxide systems with preferred orientation on an amorphous substrate via an innovative self-bilayer approach.

For the first time, this work presents a novel room temperature time-effective concept to manipulate the crystallization kinetics and magnetic responses of thin films grown on amorphous substrates.

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