Liquid Phase Epitaxy of Ferromagnetic-Piezoelectrics Heterostructures and Femto-Tesla Magnetic Sensors and Arrays

提出了一种新型压电-铁磁异质结构的研究方案，用于微型、低频、毫微特-特斯拉磁性传感器和传感器阵列，具有潜在的生物医学成像应用前景。到目前为止所研究的大多数这种磁电(ME)复合材料都结合了铁电和铁磁层，其中施加交流磁场在铁磁体中产生磁致伸缩应变，导致铁电层中的电压响应。基于铁电材料的磁电传感器具有传感器响应非线性、铁电磁滞和热释电噪声较大等缺点。这一方案是针对由La3Ga5.5Ta0.5O14(LGT)和镍锌铁氧体Ni1-xZnxFe2O4(NZFO)功能梯度铁磁层制成的磁传感器。其动机是该小组关于LGT-铁磁复合材料中ME效应的初步数据，这些数据表明：(I)在低频、弯曲和机电共振时的ME系数比具有铁电体的样品高出一到两个数量级，并且噪声要低得多，以及(Ii)预测异质结构中强烈的零偏置ME相互作用的理论模型。智能优点：计划中的方法具有多重新颖性：(I)使用预计将显示出强大的ME耦合、对交流磁场的线性电压响应和消除热释电噪声的压电式LGT，(Ii)用于自磁偏置的分级铁磁层；(Iii)用于高效应变转移的液体外延(LPE)异质结构；以及(Iv)利用微电子机械系统(MEMS)技术实现传感器和传感器阵列的小型化。主要工作包括：(I)用液相外延(LPE)法在LGT衬底上制备磁化梯度NZFO薄膜，(Ii)研究低频和共振ME相互作用，(Iii)设计和制备基于MEMS悬臂梁的铁氧体/LGT复合结构，作为谐振频率可调的磁性传感器和传感器阵列，(Iv)材料和传感器的综合表征。传感器工作在弯曲或机电共振状态时，通过频率调制可获得所需的FT灵敏度。更广泛的影响：这项研究预期的更广泛的影响包括：(1)用于不同领域的微型磁性传感器和传感器阵列，包括医学成像(心磁图和脑磁图)和安全系统。(2)材料和测量技术方面的人力资源开发和课程开发/丰富。(Iii)本科生研究训练：专业发展学院将招收理工科本科生参与研究。(四)高中生研学经历：从当地学校招收学生参加研学。

A research program is proposed on novel piezoelectric-ferromagnetic heterostructures for miniature, low-frequency, femto-Tesla magnetic sensors and sensor arrays with potential for applications in biomedical imaging. A majority of such magneto-electric (ME) composites studied so far have bonded ferroelectric and ferromagnetic layers in which an applied ac magnetic field produces magnetostrictive strain in the ferromagnet, leading to a voltage response in the ferroelectric layer. Ferroelectrics based ME sensors have several shortcomings including non-linear sensor response and considerable noise due to ferroelectric hysteresis and pyroelectric noise. This proposal is aimed at magnetic sensors made of piezoelectric lanthanum gallium tantalate, La3Ga5.5Ta0.5O14 (LGT), and functionally graded ferromagnetic layer with nickel zinc ferrite Ni1-xZnxFe2O4 (NZFO). The motivation is the group's preliminary data on ME effects in LGT-ferromagnetic composites that show (i) one to two orders of magnitude higher ME coefficients at low-frequency and at bending and electromechanical resonance, and much lower noise compared to samples with ferroelectrics, and (ii) theoretical models that predict a strong zero-bias ME interactions in the heterostructures. Intellectual Merit:The novelty in the planned approach is multifold with: (i) use of piezoelectric LGT that is expected to show strong ME coupling, linear voltage response to ac magnetic field and elimination of pyroelectric noise, (ii) graded ferromagnetic layers for self-magnetic biasing; (iii) heterostructures by liquid phase epitaxy (LPE) for efficient strain transfer; and (iv) utilization of micro-electro-mechanical systems (MEMS) technology in miniaturization of sensors and sensor arrays. Primary tasks will include (i) synthesis of magnetization-graded NZFO films on LGT substrates by liquid-phase epitaxy (LPE), (ii) studies on low-frequency and resonance ME interactions, (iii) design and fabrication of MEMS cantilever based ferrite/LGT multiple structures as resonant frequency tunable magnetic sensors and sensor array, (iv) comprehensive characterization of the materials and sensors. The desired fT-sensitivity will be achieved by frequency modulation with the sensor operating at bending or electromechanical resonance. Broader Impacts:Anticipated broader impacts of the research include the following: (i) Miniature magnetic sensors and sensor arrays for applications in diverse fields, including medical imaging (magneto-cardiography and magneto-encephalography) and security systems. (ii) Human resources development and curriculum development/enrichment in materials and measurement technologies. (iii) Undergraduate Research Training: The PIs will recruit undergraduate science and engineering majors for participation in the research. (iv) Research experience for high school students: Students from local schools will be recruited for participation in research.