Hall-Magnetometry on Ferromagnetic Micro-Rhombs

Micropatterned Hall-sensors are used to measure the magnetic switching of nanopatterned rhombic Ni-elements at temperatures below 4.2 K. The length of the short axis ('waist') was systematically varied between 700 and 100 nm while the length of 2 [micro]m of the long axis was kept fixed. The thickness of the Ni-rhombs was 70 nm. Whereas the hysteresis loops of the broader rhombs show many small steps, which seem to be connected to domain wall movement and pinning, the narrowest two only reveal one single step during magnetization reversal. The process of magnetization reversal is additionally studied by Lorentz transmission electron microscopy. Placing Hall-sensors on both ends of acicular Ni elements allows one to investigate the switching process on both sides simultaneously. Index Terms--Hall-magnetometry, individual ferromagnetic particles, magnetization reversal, micro-rhombs.