Thin Film Magnetoelectric Sensors Toward Biomagnetism: Materials, Devices, and Applications

Abstract

Since the discovery of strong magnetoelectric (ME) coupling in two‐phase ME laminate composites, strain mediated ME heterostructures have found practical applications in magnetic sensors, tunable inductors, tunable filters, miniaturized antennas, magnetic memories, and nanoscale motors. Thin film ME sensors, in particular, have become promising candidates in biomagnetic sensing, due to their high sensitivity, CMOS compatibility, room temperature operation, and high spatial resolution. In this article, an overview is presented on different types of thin film ME sensors and their applications in biomagnetic measurement. First, the coupling structures, materials selection, and fabrication processes are introduced. Three different mechanisms of recently emerged ME sensors, including the magnetic modulation, electrical modulation, and delta‐E effect are presented. Their performance and noise analysis are also compared and discussed. Finally, real‐time applications of ME sensors in the detection of magnetic fields from different part of human body are presented and discussed. The review concludes with an outlook on future perspectives and challenges of thin film ME sensors for biomagnetic applications.

Magnetoelectric MEMS Magnetic Field Sensor Based on a Laminated Heterostructure of Bidomain Lithium Niobate and Metglas

“…Among magnetic materials for the MS phase, different types of amorphous metglas alloy are generally considered [ 13 ]. FeGaC [ 14 ] and FeCoC [ 15 ] thin films exhibit the highest piezomagnetic coefficients (q) of 10 ppm/Oe.…”

“…FeGaC [ 14 ] and FeCoC [ 15 ] thin films exhibit the highest piezomagnetic coefficients (q) of 10 ppm/Oe. However, for ME MEMS, FeCoSiB with a comparable q = 5 ppm/Oe is mostly used [ 13 , 16 ]. Magnetically soft metglas thin films are most interesting for detecting ultraweak magnetic fields due to the high values of the piezomagnetic coefficient in low magnetic fields, which makes it possible to create self-biased devices [ 17 ].…”

“…The first ME CMOS-MEMS integrated sensor array showed a LOD of 16 nT/Hz 1/2 with low power consumption [ 23 ]. In the frequency range desirable for biomedical applications, ME MEMS sensors can measure magnetic fields with a sensitivity of 100 pT/Hz 1/2 [ 13 ]. Urgent tasks are to discover new promising PE and MS materials and develop fabrication processes on the MEMS scale and more accurate detection systems with fast digital signal processing.…”

A Magnetoelastic Twist on Magnetic Noise: The Connection with Intrinsic Nonlinearities

“…Other relevant sensor schemes are giant magnetoimpedance (GMI) [18][19][20] effect sensors and magnetoelectric (ME) composite sensors. [21][22][23][24][25][26] In this context, supporting flux concentrator structures [27][28][29][30] and magnetic shields [31,32] made of soft magnetic materials are also integrated into magnetic sensor structures based on non-ferromagnetic material, e.g., semiconductor-based Hall effect sensors. [33] For highly optimized XMR, GMI, and ME sensors, detectivities ≈1 pT/Hz 0.5 have been demonstrated.…”

Self‐biased magnetoelectric composite for energy harvesting

“…and utilizing energy sources from the surrounding environment, such as light, mechanical vibration, wind energy, waves, and magnetic fields. [13][14][15][16] The application of multiferroic magnetoelectric (ME) materials, which realize the mutual coupling (ME coupling effect) of ferroelectric ordering and magnetic ordering (Figure 1A), in the fields of magnetic sensors, [17][18][19][20] spintronics, [21][22][23][24] data storage, [25][26][27][28][29] and energy harvesting [29][30][31][32] can be further broadened. ME composite systems composed of piezoelectric phases (P) and magnetostrictive phases (M) and possessing strong room temperature ME coupling (high ME conversion efficiency) are drawing considerable interest in the fields of vibration energy and magnetic energy harvesting.…”