Magnetic tunnel junctions (MTJs) have exhibited significant application potential in magnetic sensors, magnetic random-access memory, spin-based logic gates, etc. However, conventional MTJ devices consisting of magnetic thin films usually suffer from interface defects and low scaling, severely compromising device performance. In contrast, all two-dimensional (2D) van der Waals (vdW) MTJs offer an effective solution to avoid these problems, due to their atomically flat surfaces, suppressed interfacial mixing, and low dimensionality. In this review, we provide a systematic overview of recent advancements in all-2D vdW MTJs involving both spin-valve and spin-filter configurations. The discussed systems are classified according to the types of 2D magnetic materials. Then, the effective strategies for modulating the performance of MTJs are introduced, such as regulating the bias voltage/current, the thickness of the tunneling layer, and spin angles. Finally, the challenges and prospects for the future development of all-2D MTJs are discussed, highlighting the potential for realizing breakthroughs in this field.

In this study, boron powder with different particle sizes was purified by both chemical and heat treatment methods. The reduction in the particle size can improve the chemical purification with no effort on the heat treatment. The superconducting properties of the powder drastically changed even with only a partial elimination of oxygen. On the one hand, less oxygen content resulted in high T_c and J_c values under the low magnetic field, and most importantly, a significant improvement in the superconducting connectivity (A_f value). On the other hand, the degradation of J_c under a high field and a change in the pinning mechanism were also found, along with decreasing oxygen. This result indicated that oxygen, probably MgO, might act as the pinning center and as an obstacle for the supercurrent in MgB₂ at the same time. This work paves the way for obtaining pure oxygen-free MgB₂ and understanding the real effect of oxygen in MgB₂.