Kerr Microscopy Imaging System Facilitates New Scientific Breakthroughs in Spintronics at Xi'an Jiaotong University

Recently, the research team from the Center for Spintronics and Quantum Systems at the School of Materials Science and Engineering, Xi'an Jiaotong University, published a highly valuable research paper in the renowned nanoscale science journal, Nanoscale (a journal of the Royal Society of Chemistry), titled "Temperature-dependent sign reversal of tunneling magnetoresistance in van der Waals ferromagnetic heterojunctions." This journal focuses on cutting-edge research areas such as nanomaterials, spintronics, and low-dimensional devices, holding significant influence within the industry. The recent publication of these findings by the Xi'an Jiaotong University team injects new vitality into the application of van der Waals magnetic heterojunctions in spintronic devices. Behind this breakthrough, the KMP-L low-temperature strong-field micro-area laser Kerr microscopy imaging system, independently developed by Truth Instruments, played a critical role. It provided direct and reliable experimental evidence for analyzing the interlayer magnetic coupling mechanism and tunneling magnetoresistance (TMR) characteristics of van der Waals ferromagnetic heterojunctions, serving as an essential characterization technique for advancing the design of spintronic devices.

The Kerr signal was characterized using a MOKE measurement system (KMP-L, Truth Instruments). The MOKE measurements were performed using a normally incident HeNe laser beam (λ = 633 nm) with linear polarization and a focused spot diameter of approximately 5 µm. During the measurements, the magnetic field was consistently applied perpendicular to the in-plane direction of the device.

Magnetic tunneling junctions (MTJs) are the core components of spintronic devices, and the control over the sign of their tunneling magnetoresistance (TMR) is crucial for expanding device functionality. In van der Waals (vdW) ferromagnetic heterojunctions, the interlayer coupling between magnetic layers and the influence of temperature on the TMR mechanism are key areas of current research. Precise characterization of micro-area magnetic domain structures and hysteresis properties is a core element in resolving these mechanisms.

The Magneto-Optical Kerr Effect (MOKE) measurement technique, especially a system that combines high-precision hysteresis loop scanning with high-resolution micro-area imaging capabilities, can directly observe magnetic domain evolution and differentiate the magnetic properties of different regions, providing indispensable experimental evidence for understanding interlayer magnetic coupling and TMR control principles.

In this paper, Truth Instruments' KMP-L low-temperature strong-field micro-area laser Kerr microscopy imaging system played a pivotal role. Through its high-resolution magnetic domain imaging function, it clearly captured the contrasting magnetic domains between the CVI-covered region and the FGT region in the CVI/FGT heterojunction at 50K, directly confirming their antiferromagnetic coupling at zero magnetic field. By utilizing its micro-area point detection capability, hysteresis loops were measured in different regions of the heterojunction (such as the CVI and FGT contact area, and the exposed FGT area), clearly distinguishing the coercive field differences between CVI and FGT and ruling out interference mechanisms like spin pinning and charge transfer. Combined with its wide temperature range testing capability, the system supported the study of TMR sign reversal and the temperature-dependent control of magnetic coupling strength by observing the subtle changes in the hysteresis loops in the critical region near the Curie temperature of CVI (60K). The KMP-L provided direct and reliable experimental evidence for analyzing the interlayer magnetic effects and TMR characteristics of the van der Waals ferromagnetic heterojunction, making it a key characterization technique for advancing the design of spintronic devices.

The characteristics of Truth Instruments' KMP-L perfectly match the demands of 2D ferromagnetic material research—"weak magnetism, small sample size, and the need for wide temperature range testing." It provides precise and reliable experimental evidence for resolving the antiferromagnetic coupling mechanism and the TMR sign reversal principle, serving as a critical link between the material's microscopic magnetic structure and the macroscopic device performance.

This collaboration once again validates the value of domestically produced high-end instrumentation—it not only provides reliable characterization support for cutting-edge scientific research but also becomes a "bridge" connecting the microscopic structure of materials to the macroscopic performance of devices. Truth Instruments will continue to deeply cultivate the characterization needs in fields suchs as low-dimensional materials and spintronics, providing researchers with more precise and efficient technical solutions to help foster more breakthrough achievements.