Browsing by Author "Li, Hao-Bo"

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Heteroepitaxy of Fe3O4/Muscovite: A New Perspective for Flexible Spintronics
(2016-12-14)
Wu, Ping-Chun
;
Chen, Ping-Fan
;
Thi Hien Do
;
Hsieh, Ying-Hui
;
Ma, Chun-Hao
Spintronics has captured a lot of attention since it was proposed. It has been triggering numerous research groups to make their efforts on pursuing spin-related electronic devices. Recently, flexible and wearable devices are in a high demand due to their outstanding potential in practical applications. In order to introduce spintronics into the realm of flexible devices, we demonstrate that it is feasible to grow epitaxial Fe3O4 film, a promising candidate for realizing spintronic devices based on tunneling magnetoresistance, on flexible muscovite. In this study, the heteroepitaxy of Fe3O4/muscovite is characterized by X-ray diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy. The chemical composition and magnetic feature are investigated by a combination of X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism. The electrical and magnetic properties are examined to show the preservation of the primitive properties of Fe3O4. Furthermore, various bending tests are performed to show the tunability of functionalities and to confirm that the heterostructures retain the physical properties under repeated cycles. These results illustrate that the Fe3O4/muscovite heterostructure can be a potential candidate for the applications in flexible spintronics.
Manipulate the Electronic and Magnetic States in NiCo2O4 Films through Electric-Field-Induced Protonation at Elevated Temperature
(2019-04-19)
Wang, Meng
;
Sui, Xuelei
;
Wang, Yujia
;
Juan, Yung-Hsiang
;
Lyu, Yingjie
Ionic-liquid-gating- (ILG-) induced proton evolution has emerged as a novel strategy to realize electron doping and manipulate the electronic and magnetic ground states in complex oxides. While the study of a wide range of systems (e.g., SrCoO2.5, VO2, WO3, etc.) has demonstrated important opportunities to incorporate protons through ILG, protonation remains a big challenge for many others. Furthermore, the mechanism of proton intercalation from the ionic liquid/solid interface to whole film has not yet been revealed. Here, with a model system of inverse spinel NiCo2O4, an increase in system temperature during ILG forms a single but effective method to efficiently achieve protonation. Moreover, the ILG induces a novel phase transformation in NiCo2O4 from ferrimagnetic metallic into antiferromagnetic insulating with protonation at elevated temperatures. This study shows that environmental temperature is an efficient tuning knob to manipulate ILG-induced ionic evolution.