Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature

Abstract

The authors observed tunnel magnetoresistance (TMR) ratio of 604% at $300\mathrm{K}$ in $\mathrm{Ta}∕{\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}∕\mathrm{Mg}\mathrm{O}∕{\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}∕\mathrm{Ta}$ pseudo-spin-valve magnetic tunnel junction annealed at $525°\mathrm{C}$ . To obtain high TMR ratio, it was found critical to anneal the structure at high temperature above $500°\mathrm{C}$ , while suppressing the Ta diffusion into CoFeB electrodes and in particular to the $\mathrm{Co}\mathrm{Fe}\mathrm{B}∕\mathrm{Mg}\mathrm{O}$ interface. X-ray diffraction measurement of MgO on $\mathrm{Si}{\mathrm{O}}_2$ or ${\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$ shows that an improvement of MgO barrier quality, in terms of the degree of the (001) orientation and stress relaxation, takes place at annealing temperatures above $450°\mathrm{C}$ . The highest TMR ratio observed at $5\mathrm{K}$ was 1144%.