Abstract
Advances in freestanding membranes allow novel heterostructures to be formed from distinct families of materials in 2D or 3D configurations. Recently, this technique has been used to form a 3D racetrack memory device by transferring a complex magnetic thin film heterostructure, in the form of a membrane, onto a corrugated surface. The membrane is released using a water-soluble oxide layer (Sr(3)Al(2)O(6)). The magnetic structure within the membrane is supported by a thin buffer layer (MgO), which decouples the magnetic structure from the receiving surface. Here it is shown that ultrathin freestanding racetrack membranes can be formed without any buffer layer and that the current-induced motion of magnetic domain walls within the transferred racetrack is highly efficient. Furthermore, the absence of any buffer layer enables local engineering of the racetracks via their direct coupling with pre-patterned platinum underlayers on which they are placed. The presence or absence of the Pt underlayer allows for local modulation of the current and field-induced manipulation of the racetrack magnetization. In addition, the ultrathin freestanding membranes exhibit excellent flexibility and enable highly reliable racetrack devices. The findings highlight the potential of freestanding magnetic heterostructure membranes for advanced spintronic applications.