Designing and implementing means of locally trapping magnetic beads and understanding the factors underlying the bead capture force are important steps toward advancing the capture-release process of magnetic particles for biological applications. In particular, capturing magnetically labeled cells using magnetic microstructures with perpendicular magnetic anisotropy (PMA) will enable an approach to cell manipulation for emerging lab-on-a-chip devices. Here, a Co (0.2 nm)/Ni (0.4 nm) multilayered structure was designed to exhibit strong PMA and large saturation magnetization (Ms). Finite element simulations were performed to assess the dependence of the capture force on the value of Ms. The simulated force profile indicated the largest force at the perimeter of the disks. Arrays of Co/Ni disk structures of (4–7) μm diameter were fabricated and tested in a microchannel with suspended fluorescent magnetic beads. The magnetic beads were captured and localized to the edge of the disks as predicted by the simulations. This approach has been demonstrated to enable uniform assembly of magnetic beads without external fields and may provide a pathway toward precise cell manipulation methods.

We explored the effect of a CoFe wedge inserted as a dusting layer (0.2 nm-0.4 nm thick) at the CoFeB/MgO interface of a sputtered Ta(2 nm)/W(3 nm)/CoFeB(0.9 nm)/MgO(3 nm)/ Ta(2 nm) film-a typical structure for spinorbit torque devices. Films were annealed at temperatures varying between 300 °C and 400 °C in an argon environment. Ferromagnetic resonance studies and vibrating sample magnetometry measurements were carried out to estimate the effective anisotropy field, the Gilbert damping, the saturation magnetization and the dead layer thickness as a function of the CoFe thickness and across several annealing temperatures. While the asdeposited films present only easyplane anisotropy, a transition along the wedge from inplane to outofplane was observed across several annealing temperatures, with evidence of a spinreorientation transition separating the two regions.

Uniform magnetic behavior within arrays of magnetoelectric heterostructures is important for the development of reliable strain-mediated microdevices. Multiple mechanisms may contribute to observed nonuniform magnetization reversal including surface roughness, non-uniform strain, and fabrication induced imperfections. Here, Co/Ni microdisks of 7 µm diameter were produced on both [Pb(Mg1/3Nb2/3)O3]1−x–[PbTiO3]x with x = 0.3 nominal composition (PMN-30PT) (011) and Si substrates, and the out-of-plane magnetization reversal was characterized using magneto-optical Kerr effect (MOKE). Coercivity variation across the microdisks within the arrays was observed on both the PMN-30PT and Si specimens with zero electric field applied. Co/Ni microdisks on a PMN-30PT substrate displayed relatively larger coercivity than those on a Si substrate due to the surface roughness effect. Quasistatic electric fields of varying magnitude were applied to the PMN-30PT substrate to assess the dependence of the coercivity on electric field induced strain. Our results indicate that while coercivity decreases with the increase of electric field induced strain, interfacial and edge roughness combine to realize a prohibitively large coercivity to overcome within the Co/Ni microdisks as well as a broad distribution of coercive field across a patterned microdisk array.

A comparative TCAD (Technology Computer Aided Design) simulation study of various 4H-SiC trench gate MOSFET (Metal Oxide Semiconductor Field Effect Transistor) (or U-shaped trench gate MOSFET abbreviated for UMOSFET) architectures for high voltage and high-speed switching applications is reported. The DC (Direct Current) and AC (Alternating Current) characteristics of the different trench gate structures are investigated. Particularly, compared to conventional 4H-SiC UMOSFETs, the breakdown voltage of the UMOSFET having a p-type implanted bottom shield is increased by 44%. However, due to the extra JFET (Junction Field Effect Transistor) region, the specific on resistance also increases by 6%. Furthermore, under 1000 V drain bias, the peak electric field at the bottom oxide of the shielded trench gate is below 0.3 MV/cm. In contrast, the peak electric field of conventional UMOSFETs can be as high as 8 MV/cm, which might cause reliability issues. On the other hand, when the bottom oxide thickness of the trench gate is increased, the UMOSFET exhibits 22% less total gate charge, leading to 76% and 71% shorter switching delay time, compared to conventional UMOSFETs and bottom shield UMOSFETs, respectively. As revealed by the simulation results, the UMOSFETs with the p-type implanted bottom shield or thick bottom oxide are advantageous for high voltage and high-speed power switching applications.