Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

Kyoung-Min Lee,Junghyun Sok,Jun Woo Choi,Byoung-Chul Min

doi:10.1063/1.4985720

Abstract

The interfacial perpendicular magnetic anisotropy in W/CoFeB (1.2 ∼ 3 nm)/MgO thin film structures is strongly dependent on temperature, and is significantly reduced at high temperature. The interfacial magnetic anisotropy is generally proportional to the third power of magnetization, but an additional factor due to thermal expansion is required to explain the temperature dependence of the magnetic anisotropy of ultrathin CoFeB films. The reduction of the magnetic anisotropy is more prominent for the thinner films; as the temperature increases from 300 K to 400 K, the anisotropy is reduced ∼50% for the 1.2-nm-thick CoFeB, whereas the anisotropy is reduced ∼30% for the 1.7-nm-thick CoFeB. Such a substantial reduction of magnetic anisotropy at high temperature is problematic for data retention when incorporating W/CoFeB/MgO thin film structures into magneto-resistive random access memory devices. Alternative magnetic materials and structures are required to maintain large magnetic anisotropy at elevated temperatures.

Highlights

One of the requirements for widespread use of STT-MRAM in commercial electronic devices is that the device performances, such as tunnel magnetoresistance (TMR)
CoFeB/MgO thin films have been extensively utilized in STT-MRAMs since the discovery of interfacial perpendicular magnetic anisotropy (PMA) and high TMR in such systems.[12,13]
We investigated the temperature dependence of PMA energy of the W/CoFeB/MgO thin film system in the temperature range of 1.8 ∼ 400 K

Summary

Introduction

The spin transfer torque magneto-resistive random access memory (STT-MRAM) using magnetic tunnel junctions (MTJs) is one of the most promising candidates for generation non-volatile memory with high density and low power consumption.[1,2] In particular, MTJs with perpendicularlymagnetized ferromagnetic electrodes have several important advantages such as high thermal stability and low write current density.[3,4,5] One of the requirements for widespread use of STT-MRAM in commercial electronic devices is that the device performances, such as tunnel magnetoresistance (TMR). Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

Results

Conclusion