Exploring the Role of Interfacial Dzyaloshinskii-Moriya Interaction in Write Error Rate Anomalies of Spin-Transfer Torque Magnetic Tunnel Junctions

TL;DR

This paper investigates how interfacial Dzyaloshinskii-Moriya interaction influences write error rate anomalies in STT-MRAM, revealing that DMI causes incoherent switching and intermediate states, which can be mitigated by longer pulses.

Contribution

The study demonstrates the impact of interfacial DMI on WER anomalies in MTJs through micromagnetic simulations, highlighting interfacial engineering as a strategy for reliability improvement.

Findings

DMI promotes incoherent magnetization reversal.

High DMI values lead to persistent intermediate states.

Longer switching pulses reduce WER anomalies.

Abstract

The performance and reliability of spin-transfer torque magnetic random-access memory (STT-MRAM) can be compromised by anomalous switching behavior, especially during high-speed operations. One such anomaly, known as the "ballooning effect" is characterized by an unexpected non-monotonic increase in the write error rate (WER) with increase in STT current at specific current pulse durations. In this study, we systematically investigate the role of the interfacial Dzyaloshinskii-Moriya interaction (DMI) on such WER anomaly using micromagnetic simulations of 20 nm and 50 nm magnetic tunnel junctions (MTJs). We show that DMI promotes incoherent magnetization reversal, prolongs the switching time and creates intermediate multidomain states that result in incomplete reversal. At high DMI values, these states persist even under large switching current densities, reproducing ballooning-like anomalies reported experimentally. In contrast, longer pulses overcome these effects by allowing the system sufficient time to reach a stable state. Our findings show that interfacial DMI can play a role in the ballooning effect and point to interfacial engineering as a practical strategy for improving the reliability of next-generation STT-MRAM.