Voltage-induced switching of nanoscale magnetic tunnel junctions

We demonstrate voltage-induced (non-STT) switching of nanoscale, high resistance voltage-controlled magnetic tunnel junctions (VMTJs) with pulses down to 10 ns. We show ∼10x reduction in switching energies (compared to STT) with leakage currents < 10⁵ A/cm². Switching dynamics, from quasi-static to the nanosecond regime, are studied in detail. Finally, a strategy for eliminating the need for external magnetic-fields, where switching is performed by set/reset voltages of different amplitudes but same polarity, is proposed and verified experimentally.

Introduction

Magnetic tunnel junctions (MTJs) have emerged as the building blocks of spintronic circuits due to their large tunneling magnetoresistance (TMR) ratios, and the possibility of integration with conventional semiconductor electronics. The use of spin-polarized currents to switch magnetization in MTJs, e.g., via spin-transfer-torque (STT), however, limits the energy efficiency and density of STT-based MRAM, due to Ohmic losses and the need for large transistors to drive the required switching current, respectively (1). Therefore, electric-field control of magnetism could result not only in a magnetoelectric random access memory (MeRAM) with improved energy efficiency and density compared to STT-RAM, but also in new applications for nonvolatile spintronic devices, by making them energetically competitive compared to traditional semiconductor solutions for logic and computation.