## 1 Introduction
Early detection methods for biological magnetic fields involve the development of highly sensitive tools, such as superconducting quantum interference devices (SQUIDs) [30], atomic magnetometers [31], and fluxgates [32], which can detect similar weak magnetic signals. However, the clinical application of human magnetic field detection is not yet widespread due to cost and technical limitations [33]. There have been studies on weak magnetic sensors based on the magnetostrictive effect, specifically targeting the human body's magnetic field, including brain magnetic fields [34; 35], muscle magnetic fields [36], and cardiac magnetic fields [37]. Many magnetic field sensors that combine SAWS with magnetostrictive materials rely on the delta-E effect [38; 39]. The delta-E effect, generated by inverse magnetostriction, introduces additional strain beyond the pure elastic Hooke strain, typically occurring in multiple components of the elastic modulus and elastic stiffness tensor [40]. This paper proposes a novel approach that couples SAWS and magnetostrictive materials in a two-dimensional planar configuration, harnessing the sensing capability of the piezoelectric substrate to detect stress in the lateral direction for magnetic field measurement. Sensing the cardiac magnetic field is challenging, as is the selective detection of different cardiac parameters with a single sensor. Selective sensors enable higher integration in medical devices, reducing the need for multiple sensing modules and facilitating miniaturization and cost reduction. As some cardiac parameters interrelate, advanced designs are crucial for selective detection. In the field of acoustics, longitudinal critically refracted (LCR) waves also have potential applications in detection and sensing. For instance, LCR waves can be utilized for stress analysis or non-destructive testing [41; 42]. For the study of acoustic issues, establishing numerical models and using simulation software is an effective solution [43]. Inthe research of the LCR wave, inputting the proposed numerical model into simulation software provides significant preliminary support for analyzing problems [44]. Similar solutions can be applied to the simulation studies of SAWSs. To analyze the SAWS, the finite element analysis method is employed, establishing a model to examine its resonant frequency, resonant mode, admittance curve, S parameter curve, and mechanical quality factor. Furthermore, this paper performs tests on noise resistance, stress, and thermal factors to explore how the resonant frequency of the multi-parameter sensor based on Surface Acoustic Wave Sensors (MP-SAWSs) correlates with different physical variables. Finally, the magnetic field sensing characteristics of MP-SAWS are explored, and the sensor is validated by comparing it with existing data in the database. In this paper, an MP-SAWS is simulated and designed, taking advantage of SAWS's high sensitivity and adaptability. The proposed approach involves integrating lithium niobite (LiNbO\({}_{3}\)) piezoelectric film and magnetostrictive material Terfenol-D into a sensing array [45]. Compared to traditional magnetic field sensors, the designed SAWS offers a wider range of applications due to its wireless and passive characteristics. Novel sensors can achieve selective measurements through the control variable method. It has the ability to adjust to diverse work settings and fulfill a range of demands, even in challenging conditions. Compared to existing sensors, this sensor offers a solution for multi-parameter sensing with selectivity. Achieving selective sensing using a single device is more conducive to integrated design. The approach to enabling multiple sensing capabilities provides more possibilities for the design of new sensors.