Heteroepitaxially flexible oxide systems have been intensely developed and considered as the most promising materials for leading the creation of next-generation flexible electronic devices. Among them, perovskite manganites have attracted significant attention with their abundant and novel properties such as colossal magnetoresistance (CMR) and metal-insulator transition. However, the requirement of high quality samples hampers this field, not to mention the advanced nanoengineering. In this study, fluorophlogopite mica (F-mica) is selected as a flexible substrate to fabricate heteroepitaxial Pr 0.5 Ca 0.5 MnO 3 (PCMO) with a nanocolumn structure. Through a precise control of thickness, different morphologies are realized to manipulate the magnetotransport properties (reduction of melting field). Moreover, thanks to the excellent flexibility of F-mica, mechanical modulation of CMR (≈1000%) can be achieved in different flex modes while the magnetic properties remain unaffected. Detailed bending tests are performed to study the behavior of resistive change (≈30%). Through the combination of high flexibility, high quality PCMO, and well-designed nanocolumn structure, the study exhibits the significant controllability of CMR via mechanical bending, and manifests the potential of such a heteroepitaxially flexible oxide system which can be applied on flexible magnetoresistive devices and sensors.
The piezoresistive effect has shown a remarkable potential for mechanical sensor applications and been sought for its excellent performance. A great attention was paid to the giant piezoresistive effect and sensitivity delivered by silicon-based nanostructures. However, low thermal stability and complicated fabrication process hinder their practical applications. To overcome these issues and enhance the functionalities, we envision the substantial piezopotential in a zinc oxide (ZnO)/muscovite (mica) heteroepitaxy system based on theoretical consideration and realize it in practice. High piezoresistive effect with giant change of resistivity (−80 to 240%) and large gauge factor (>1000) are demonstrated through mechanical bending. The detailed features of heteroepitaxy, electrical transport, and strain are probed to understand the mechanism of such a giant resistivity change. In addition, a bending model is established to reveal the distribution of strain. Finally, we demonstrate a flex sensor featuring high sensitivity, optical transparency, and two-segment sensing with a great potential toward practical applications. Such an oxide heteroepitaxy exhibits excellent piezoresistive properties and mechanical flexibility. In the near future, the importance of flex sensors will emerge because of the precise control in the automation industries, and our results lead to a new design in the field of flex sensors.
Materials
with high spin-polarization play an important role in
the development of spintronics. Co-based Heusler compounds are a promising
candidate for practical applications because of their high Curie temperature
and tunable half-metallicity. However, it is a challenge to integrate
Heusler compounds into thin film heterostructures because of the lack
of control on crystallinity and chemical disorder, critical factors
of novel behaviors. Here, muscovite is introduced as a growth substrate
to fabricate epitaxial Co2MnGa films with mechanical flexibility.
The feature of heteroepitaxy is evidenced by the results of X-ray
diffraction and transmission electron microscopy. Moreover, high chemical
ordering with superior properties is delivered according to the observation
of large Hall conductivity (680 Ω–1 cm–1) and highly saturated magnetic moment (∼3.93
μB/f.u.), matching well with bulk crystals. Furthermore,
the excellence of magnetic and electrical properties is retained under
the various mechanical bending conditions. Such a result suggests
that the development of Co2MnGa/muscovite heteroepitaxy
provides not only a pathway to the thin film heterostructure based
on high-quality Heusler compounds but also a new aspect of spintronic
applications on flexible substrates.
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