Magnetization Reversal of Individual 3D Nanostructures

Driven by the quest for novel magnetic phenomena, there is an ongoing effort dedicated to expand 2D nanomagnetism to the third dimension where spin textures extend into the vertical direction of the substrate plane, thereby creating more complex ferromagnetic properties and opening the door for a fascinating new research area. This idea recently became viable by the advent of advanced fabrication methods such as the direct-write process FEBID (focused electron beam induced deposition) and the possibility of high-resolution detection of small magnetic signals, e.g. using a home-built micro-Hall sensor. In a recent work [1,2], and in this presentation, we discuss first insights into the magnetic properties of nano-engineered 3D CoFe structures, which have been deposited using FEBID directly on the sensor’s surface. Firstly, we report systematic measurements of the magnetic stray fields of nano-cube (see Figure 1) and tetrahedral nano-tree structures as a function of temperature and magnetic field angle. We compare the experimental findings to both macro-spin and micro-magnetic simulations in order to unveil the complex switching behaviour and mechanism of magnetization reversal. This combination of methods reveals a reversal of the edge spin textures proceeding via complex vortex configurations. Secondly, in order to gain further insights in the hysteresis loops, (irreversible) magnetic interaction effects and coercivity distributions we present first-order-reversal curves (FORC) of these 3D nanomagnets supported by simulations of a simple macro-spin model. We give an outlook to the future design of such structures towards the realization of 3D artificial spin ice architectures. Keywords: 3D nanomagnetism, 3D nano-architectures, focused electron beam induced deposition (FEBID), micro-Hall magnetometry, Macro-magnetic simulation, Micro-magnetic simulation, First order reversal curves Ref. [1] Keller, et al. Scientific Reports (2018) [2] M. K.I. Al Mamoori et al., Materials 11, 289 (2018).