Spin transfer torque programming dipole coupled nanomagnet arrays

Abstract

We experimentally demonstrated spin transfer torque (STT) programming of dipole coupled nanomagnets using magnetic tunnel junctions. The STT write operations were performed in conjunction with a clock field used in magnetic quantum cellular automata (MQCA) operations. The spacing and number of nanomagnets in the transmission line strongly affected the STT programming of the individual pillars. These MQCA transmission lines ranged in length from 2 elements to 20 elements, while device sizes ranged between 50 nm × 80 nm and 70 nm × 100 nm with spacing between 10 nm and 15 nm. With the application of the clock field, currents of 100-200 μA are sufficient to STT program the device. The demonstration of STT programming of individual nanomagnets in a dipole coupled array marks a significant step forward for applications such as MQCA logic device.

Spin-torque building blocks

“…Most of these concepts, such as domain wall logic [67], all spin logic [68] or nanomagnet logic whether planar [69], vertical [70] or at the atomic-scale level [71], rely on interacting devices arrays. The information, encoded in the magnetization state of nanomagnets, is read through magnetoresistive effects while spin torque is seen as the ideal replacement to field writing [72].…”

Controlling vortex chirality in hexagonal building blocks of artificial spin ice

“…We demonstrate the reliable and robust creation of vortices in such structures at the same length scale as that of vortex states in continuous rings [4,19,20], but in contrast to rings our structures can be scaled down, and maintaining the geometric aspect ratio of all islands the structures remain operative at the smallest length scales given sufficiently low temperatures. Previously, such arrays of dipolar coupled elements [14,21,22] have been proposed for logic devices [23,24] including individual addressing of islands [25], but in general typical disorder yielded substantial error rates [24]. Here we show that this error rate can be reduced to close to zero by replacing selected islands with narrower ones having higher switching fields.…”

Nanomagnet Logic Gate With Programmable-Electrical Input

“…The large dimensions of nanomagnets in the experiment resulted in higher clock and bias field requirements, but was necessary for reliable MFM imaging. The implementation of an NML output using a magnetoresistive device [17], input using spin torque device [13], and reduction of clock field using enhanced permeability dielectric (EPD) [18] could lead to a more energy-efficient and scalable NML system in the future.…”

“…A field-coupled electrical input was demonstrated on coupled nanomagnets [11] and NML data lines [12]. Spin torque-based NML input with improved scalability was suggested in [13]. However, a demonstration of an NML system at the gate level with on-chip clock and integrated input/output is yet to be realized.…”