  Neuromorphic computing (NC) is considered as a potential vehicle for
implementing energy-efficient artificial intelligence (AI). To realize NC,
several materials systems are being investigated. Among them, the spin-orbit
torque (SOT) -driven domain wall (DW) devices are one of the potential
candidates. To implement these devices as neurons and synapses, the building
blocks of NC, researchers have proposed different device designs. However, the
experimental realization of DW device-based NC is only at the primeval stage.
In this study, we have proposed and investigated pine-tree-shaped DW devices,
based on the Laplace force on the elastic DWs, for achieving the synaptic
functionalities. We have successfully observed multiple magnetization states
when the DW was driven by the SOT current. The key observation is the
asymmetric pinning strength of the device when DW moves in two opposite
directions (defined as, xhard and xeasy). This shows the potential of these DW
devices as DW diodes. We have used micromagnetic simulations to understand the
experimental findings and to estimate the Laplace pressure for various design
parameters. The study leads to the path of device fabrication, where synaptic
properties are achieved with asymmetric pinning potential.
