1. Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
2. ERATO Semiconductor Spintronics Project, Japan Science and Technology Agency, Japan

Correspondence to: H. Ohno^1,2 Email: ohno@riec.tohoku.ac.jp

Abstract

Magnetic information storage relies on external magnetic fields to encode logical bits through magnetization reversal. But because the magnetic fields needed to operate ultradense storage devices are too high to generate, magnetization reversal by electrical currents is attracting much interest as a promising alternative encoding method. Indeed, spin-polarized currents can reverse the magnetization direction of nanometre-sized metallic structures through torque^{1, 2, 3, 4}; however, the high current densities of 10⁷–10⁸ A cm^-2 that are at present required exceed the threshold values tolerated by the metal interconnects of integrated circuits^{5, 6}. Encoding magnetic information in metallic systems has also been achieved by manipulating the domain walls at the boundary between regions with different magnetization directions^{7, 8, 9, 10, 11, 12, 13}, but the approach again requires high current densities of about 10⁷ A cm^-2. Here we demonstrate that, in a ferromagnetic semiconductor structure, magnetization reversal through domain-wall switching can be induced in the absence of a magnetic field using current pulses with densities below 10⁵ A cm^-2. The slow switching speed and low ferromagnetic transition temperature of our current system are impractical. But provided these problems can be addressed, magnetic reversal through electric pulses with reduced current densities could provide a route to magnetic information storage applications.

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