Mechanical Strain‐Tunable Microwave Magnetism in Flexible CuFe₂O₄ Epitaxial Thin Film for Wearable Sensors

Abstract

Purely mechanical strain-tunable microwave magnetism device with lightweight, flexible, and wearable is crucial for passive sensing systems and spintronic devices (noncontact), such as flexible microwave detectors, flexible microwave signal processing devices, and wearable mechanics-magnetic sensors. Here, a flexible microwave magnetic CuFe 2 O 4 (CuFO) epitaxial thin film with tunable ferromagnetic resonance (FMR) spectra is demonstrated by purely mechanical strains, including tensile and compressive strains, on flexible fluorophlogopite (Mica) substrates. Tensile and compressive strains show remarkable tuning effects of up-regulation and down-regulation on in-plane FMR resonance field (H r ), which can be used for flexible tunable resonators and filters. The out-of-plane FMR spectra can also be tuned by mechanical bending, including H r and absorption peak. The change of out-of-plane FMR spectra has great potential for flexible mechanics-magnetic deformation sensors. Furthermore, a superior microwave magnetic stability and mechanical antifatigue character are obtained in the CuFO/Mica thin films. These flexible epitaxial CuFO thin films with tunable microwave magnetism and excellent mechanical durability are promising for the applications in flexible spintronics, microwave detectors, and oscillators.

Atomic Scale Understanding of the Epitaxy of Perovskite Oxides on Flexible Mica Substrate

“…Very recently, intensive research has been devoted to such epitaxial growth of functional perovskite and spinel oxides films on mica for flexible devices . For perovskite SrRuO 3 film system, the crystallographic orientation relationship between films and mica substrate was determined as {111} films || (001) mica and 〈01〉 films || [010] mica by X‐ray diffraction (XRD) .…”

A Strategy to Modulate the Bending Coupled Microwave Magnetism in Nanoscale Epitaxial Lithium Ferrite for Flexible Spintronic Devices

“…For flexible spintronics based applications, magnetic materials with high spin polarization as well as excellent mechanical flexibility are highly desirable to meet the requirement of high performance and stability . In the previous studies, bending‐deformation‐related magnetic hysteresis (M‐H) loops have been found in several flexible epitaxial oxide thin films with high crystalline quality, such as CoFe 2 O 4 , CuFe 2 O 4 , LiFe 5 O 8 , Fe 3 O 4 , etc. The results indicate that the effects of bending‐induced mechanical strains on the magnetic properties are different for different materials.…”

Magnetic properties of synthetic fluorophlogopite mica crystals

“…22 In this context, the integration of magnetic materials on mica is also gaining importance. [23][24][25][26] In parallel, the interest in magnetic 2D materials has been spurred by the recent discovery of this property, either intrinsic or associated to defects, in some of this low dimensional systems. 27,28 Despite the relevance of mica as substrate for growing magnetic materials, not enough attention has been paid to the magnetic properties of mica itself.…”

“…As a result, it has increasingly been the substrate of choice for the development of new functional materials. 26,[37][38][39] Yet, the fundamental understanding of this fluorine-rich silicate is far from complete. This is particularly true concerning the magnetic properties which, to our knowledge, were only qualitatively studied by Tsui et al 40 on the fluoromica samples prepared in their laboratory to be used as substrates to grow rare earth films.…”