Magnetic Straintronics by Supriyo Bandyopadhyay

Author:Supriyo Bandyopadhyay
Language: eng
Format: epub
ISBN: 9783031206832
Publisher: Springer International Publishing

All nanomagnets’ magnetizations are initially aligned in the same direction with a strong magnetic field which enforces ferromagnetic ordering (nearest neighbors have parallel magnetizations), as shown in the top row of Fig. 6.6a. To achieve the anti-ferromagnetic ordering shown in the top row of Fig. 6.5, one proceeds as follows: At first a high global stress is applied which can invert the energy barriers in the two right nanomagnets in Fig. 6.6a and make their magnetizations align along the hard axis, but not in the far left nanomagnet which has the highest eccentricity and hence the largest energy barrier. Its magnetization remains aligned along its major axis. This is shown in the second row of Fig. 6.6a. Then the stress is reduced to an intermediate value which can keep the energy barrier in the far right nanomagnet inverted but not in the middle one. The magnetization of the former therefore remains aligned along its hard axis, but the magnetization of the latter rotates away from the hard axis and aligns along the easy axis. Because of unequal dipole interaction from the left and right neighbors, it aligns antiparallel to the magnetization of the left nanomagnet. This is shown in the third row of Fig. 6.6a. Finally, the global stress is withdrawn and now the far right nanomagnet also has to align along its easy axis (major axis), but because of the dipole influence of its left neighbor, it assumes an orientation that is antiparallel to that of the left neighbor. This is shown in the bottom row of Fig. 6.6. This, of course, restores that anti-ferromagnetic ordering which will ensure that the bit encoded in the first nanomagnet in the left is repeated in every odd-numbered nanomagnet and the input bit has propagated unidirectionally down the chain from left to right.

Figure 6.6b shows magnetic force micrographs of 12 trios of elliptical Co nanomagnets with decreasing eccentricity from left to right. The left panel shows the pre-stress condition where all magnetizations point in the same direction because a strong magnetic field has magnetized them in that direction. The right panel shows the states after the stress sequence: high, intermediate, relax. Four out of the 12 chains show restoration of the anti-ferromagnetic ordering and hence successful Bennett clocking. Again, the success rate is low, much lower than 50%, which once again confirms that dipole coupled straintronic logic is error-prone.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.