Magnetic Field Sensing by Exploiting Giant Nonstrain-Mediated Magnetodielectric Response in Epitaxial Composites.

Heteroepitaxial magnetoelectric (ME) composites are promising for the development of a new generation of multifunctional devices, such as sensors, tunable electronics, and energy harvesters. However, challenge remains in realizing practical epitaxial composite materials, mainly due to the interfacial lattice misfit strain between magnetostrictive and piezoelectric phases and strong substrate clamping that reduces the strain-mediated ME coupling. Here, we demonstrate a nonstrain-mediated ME coupling in PbZr0.52Ti0.48O3 (PZT)/La0.67Sr0.33MnO3 (LSMO) heteroepitaxial composites that resolves these challenges, thereby, providing a giant magnetodielectric (MD) response of ∼27% at 310 K. The factors driving the magnitude of the MD response were found to be the magnetoresistance-coupled dielectric dispersion and piezoelectric strain-mediated modulation of magnetic moment. Building upon this giant MD response, we demonstrate a magnetic field sensor architecture exhibiting a high sensitivity of 54.7 pF/T and desirable linearity with respect to the applied external magnetic field. The demonstrated technique provides a new mechanism for detecting magnetic fields based upon the MD effect.

Correlation between tunability and anisotropy in magnetoelectric voltage tunable inductor (VTI).

Electric field modulation of magnetic properties via magnetoelectric coupling in composite materials is of fundamental and technological importance for realizing tunable energy efficient electronics. Here we provide foundational analysis on magnetoelectric voltage tunable inductor (VTI) that exhibits extremely large inductance tunability of up to 1150% under moderate electric fields. This field dependence of inductance arises from the change of permeability, which correlates with the stress dependence of magnetic anisotropy. Through combination of analytical models that were validated by experimental results, comprehensive understanding of various anisotropies on the tunability of VTI is provided. Results indicate that inclusion of magnetic materials with low magnetocrystalline anisotropy is one of the most effective ways to achieve high VTI tunability. This study opens pathway towards design of tunable circuit components that exhibit field-dependent electronic behavior.

Switchable 3-0 magnetoelectric nanocomposite thin film with high coupling.

A mixed precursor solution method was used to deposit 3-0 nanocomposite thin films of PbZr0.52Ti0.48O3 (PZT) and CoFe2O4 (CFO). The piezoelectric behavior of PZT and magnetostrictive behavior of CFO allow for magnetoelectric (ME) coupling through strain transfer between the respective phases. High ME coupling is desired for many applications including memory devices, magnetic field sensors, and energy harvesters. The spontaneous phase separation in the 3-0 nanocomposite film was observed, with 25 nm CFO particle or nanophases distributed in discrete layers through the thickness of the PZT matrix. Magnetic-force microscopy images of the nanocomposite thin film under opposite magnetic poling conditions revealed in-plane pancake-like regions of higher concentration of the CFO nanoparticles. The constraints on the size and distribution of the CFO nanoparticles created a unique distribution in a PZT matrix and achieved values of ME coupling of 3.07 V cm-1 Oe-1 at a DC bias of 250 Oe and 1 kHz, increasing up to 25.0 V cm-1 Oe-1 at 90 kHz. Piezo-force microscopy was used to investigate the ferroelectric domain structure before and after opposite magnetic poling directions. It was found that in this nanocomposite, the polarization of the ferroelectric domains switched direction as a result of switching the direction of the magnetization by magnetic fields.