Composition Regulation and Microstructure Characterization of Fe100-xGax Films in the Manufacturing Industry

Fe100-xGax giant magnetostrictive films (GMF) are attracting ever increasing attention for their potential application to manufacturing integrated magnetostrictive displacement sensors. However, it is difficult to fabricate Fe100-xGax thin films with different compositions at will. The influence of compositions on alloy phases, grain sizes, film surface roughness, and magnetic domains of the films and magnetization of magnetron sputtered Fe100-xGax films was investigated. Changing the ratio of the pure iron slice areas to alloy target areas, the desired film composition was achieved by the improved Mosaic method. The morphologies, magnetic domain structure, microstructure, and compositions of Fe100-xGax films revealed by SEM, EDS, XRD, MFM, VSM, and TEM. The results show that there are <1 1 0 > texture in magnetron sputtered Fe100-xGax films. The sharp peak attributed to the A2 microstructure suggests that the film is crystalline. The magnetic domain structure of Fe100-xGax films presents a network form, and the domain width decreases with the decrease of gallium content. It is also found that the magnetic domains of the films are not uniform. The TEM result shows that there are some strip patterns in the films, and the diffraction ring is discontinuous because of the structure extinction. For a suitable candidate of microdevice applications in MEMS, the optimum composition film should be Fe83.25Ga16.75 film.

Unconventional supercurrent phase in Ising superconductor Josephson junction with atomically thin magnetic insulator

In two-dimensional (2D) NbSe2 crystal, which lacks inversion symmetry, strong spin-orbit coupling aligns the spins of Cooper pairs to the orbital valleys, forming Ising Cooper pairs (ICPs). The unusual spin texture of ICPs can be further modulated by introducing magnetic exchange. Here, we report unconventional supercurrent phase in van der Waals heterostructure Josephson junctions (JJs) that couples NbSe2 ICPs across an atomically thin magnetic insulator (MI) Cr2Ge2Te6. By constructing a superconducting quantum interference device (SQUID), we measure the phase of the transferred Cooper pairs in the MI JJ. We demonstrate a doubly degenerate nontrivial JJ phase (ϕ), formed by momentum-conserving tunneling of ICPs across magnetic domains in the barrier. The doubly degenerate ground states in MI JJs provide a two-level quantum system that can be utilized as a new dissipationless component for superconducting quantum devices. Our work boosts the study of various superconducting states with spin-orbit coupling, opening up an avenue to designing new superconducting phase-controlled quantum electronic devices.

Vector analysis of electric-field-induced antiparallel magnetic domain evolution in ferromagnetic/ferroelectric heterostructures

Electric field (E-field) control of magnetism based on magnetoelectric coupling is one of the promising approaches for manipulating the magnetization with low power consumption. The evolution of magnetic domains under in-situ E-fields is significant for the practical applications in integrated micro/nano devices. Here, we report the vector analysis of the E-field-driven antiparallel magnetic domain evolution in FeCoSiB/PMN-PT(011) multiferroic heterostructures via in-situ quantitative magneto-optical Kerr microscope. It is demonstrated that the magnetic domains can be switched to both the 0° and 180° easy directions at the same time by E-fields, resulting in antiparallel magnetization distribution in ferromagnetic/ferroelectric heterostructures. This antiparallel magnetic domain evolution is attributed to energy minimization with the uniaxial strains by E-fields which can induce the rotation of domains no more than 90°. Moreover, domains can be driven along only one or both easy axis directions by reasonably selecting the initial magnetic domain distribution. The vector analysis of magnetic domain evolution can provide visual insights into the strain-mediated magnetoelectric effect, and promote the fundamental understanding of electrical regulation of magnetism.