We developed a three-terminal spintronic memristor named spin-memristor for the artificial synapse of neuromorphic devices. Current-induced domain wall (DW) motion type magnetoresistance was used to generate variable analog conductance changes. Magnetic tunnel junction with a perpendicularly magnetized DW layer was fabricated on a silicon substrate. Due to the forward and backward DW motions, a linear and symmetric conductance response was achieved. The impact of memristive behavior on neural networks was evaluated using numerical simulation of hand-written digit recognition. This spin-memristor is identified as one of the promising candidates for artificial synapses in analog neuromorphic devices.

We measured the temperature dependence of the photocurrent in an organic Mott‐insulator β′‐(bis(ethylenedithio)‐tetrathiafulvalene)(7,7,8,8‐tetracyanoquinodimethane) (BEDT‐TTF)(TCNQ) crystal with applied bias voltage along the c‐ and b‐axis up to 12 V. A semiconductor laser with a wavelength of 405 nm was used as the light source. We observed that with increasing bias voltage, the temperature at which the photocurrent starts to flow decreases down to 16 K, near the antiferromagnetic (AF) transition temperature of BEDT‐TTF (TN = 20 K). This result indicates that the AF transition plays an important role in the suppression of photogenerated carrier conduction. The creation of strongly bound holon–doublon clusters, which are expected to exist in the AF spin order states, is identified as one of the factors responsible for the photocurrent suppression. Above the TN, it was confirmed that both the photogenerated electron and hole can be comparably detected as the photocurrent by changing the polarity of the bias voltage.

Spin-memristors using a magnetic domain wall (DW) have drawn attention as possible candidates for an essential element of the analogue neuromorphic device. In this study, we fabricated a DW type three-terminal magnetic tunneling junction element with a magnetic fixed region having a synthetic antiferromagnetic configuration. The DW creation and subsequent measurement of current-induced domain wall motion were investigated. The magnetic DW was successfully introduced through a simple operation using the magnetic fixed region as a DW injector. This element structure will be one of the key technologies for realizing an array level production of the spin-memristor.