Figure 1
(a) An N by N network of spins to represent an N city traveling salesman problem (here N = 4). Each spin, x u,i denotes whether city u should be visited at order i, where the rows represent the cities and the columns stand for the order of visit. In this work, we have assigned the binary values ‘1’ and ‘0’ to ‘up’ (magnetization moment, x u,i = +1) and ‘down’ (x u,i = −1) spin states, respectively. This conversion from bipolar to binary variables is shown in the table. (b) The geometry of the device representing each spin unit. Input voltage, V IN is applied across a multiferroic oxide/CoFeB heterostructure, labeled as the ‘Write’ unit. The magnetization moment of this CoFeB layer depicts x u,i which can point along +z (‘up’) or −z (‘down’) direction (easy axes) under the magnetoelectric effect. A voltage divider circuit, which is the ‘Read’ unit, consists of a resistance, R REF and an MTJ. This ‘Read’ unit is electrically separated from the oxide/nanomagnet stack, but are magnetically coupled by dipolar interaction. The voltage across the MTJ, V OUT changes depending on the state of x u,i . (c) The switching probability curve of the CoFeB layer vs V IN . The magnetization moment vs time plots are shown in the insets at positive (C), negative (A) and zero (B) input voltages.
