Research Projects

Magnetic sensors are crucial in various applications, which include space navigation, defense applications, automotive, biomedical applications, and industrial automation. Several approaches exist to develop magnetic sensors based on the ordinary Hall effect, spin-dependent resistance effect, and superconducting quantum interference devices. Furthermore, these sensors produce output along a specific axis, creating a one-dimensional sensor. However, three-dimensional (3D) sensing is necessary for various automation and industrial applications. The traditional method of detecting the magnetic field in three dimensions involves placing three Hall sensors orthogonally, i.e., along the x, y, and z directions. This requires additional experimental setup and complicates magnetic field sensing due to the cross-sensitivity among the measurement axes. Hence, developing a compact device that can function as a 3D sensor is crucial. The recent advancements in the spin Hall effect have opened up possibilities for developing a 3D magnetic sensor. The spin Hall effect converts a longitudinal charge current density into a transverse spin current density due to the spin-orbit coupling. The spin current, typically generated in heavy metals and antiferromagnets, is beneficial for switching a nearby perpendicularly magnetized layer. This spin current applies torque on the proximal magnetized layer, known as spin-orbit torque. Spin current-induced spin-orbit-torque can switch the magnetized layer in the presence of in-plane bias fields, leading to the development of a sensing device to measure the 3D magnetic field. In this proposal, we will focus on developing a 3D sensor using thin bilayer films of Mn₃SnN and Mn₄N and heterostructures of Mn₃SnN and (Co/Ni)₃. Mn₃SnN is a non-collinear antiferromagnet with zero net magnetization and can generate spin currents with polarizations along the x, y, and z directions. Here, we will utilize the y-polarized spin currents to generate spin-orbit torque, which can be employed to switch the magnetization of either the ferrimagnet Mn₄N or the ferromagnet (Co/Ni)₃. In current-induced magnetization switching, we measure the anomalous Hall resistance (R_xy) as a function of current (J_x) for a fixed bias field (H_x) using a symmetric Hall bar. The polarity of the deterministic spin-orbit torque-induced magnetization switching will change when the sign of the external bias field is altered. The relationship between R_xy (R_yx) and H_x, H_y, H_z for a fixed critical current J_x ( J_y) can be utilized to detect 3D magnetic fields. The development of such a 3D magnetic sensor is currently in its preliminary stages. The sensor's sensitivity, dynamic range, and robustness remain open questions that can be enhanced by researching various magnetic materials. This enhances our fundamental understanding of the 3D sensor and aids in commercializing the product.