Fabrication of high-magnetoresistance tunnel junctions using Co75Fe25 ferromagnetic electrodes

Abstract

Temperature dependence of tunnel magnetoresistance (TMR) ratio, resistance, and coercivity from 4.2 K to room temperature and applied voltage dependence of the TMR ratio and resistance at room temperature for a tunnel junction, Ta (5 nm)/Ni79Fe21 (3 nm)/Cu (20 nm)/Ni79Fe21 (3 nm)/Ir22Mn78 (10 nm)/Co75Fe25 (4 nm)/Al (0.8 nm)-oxide/Co75Fe25 (4 nm)/Ni79Fe21 (20 nm)/Ta(5 nm), were investigated. TMR ratio, effective barrier height and width, and breakdown voltage of the junction can be remarkably enhanced after annealing at 300 °C for an hour. High TMR ratio of 49.7% at room temperature and 69.1% at 4.2 K were observed. The value of spin polarization of Co75Fe25, P=50.7%, deduced from the TMR ratio at 4.2 K was corresponding well to the experimental data measured at 0.2 K in a spin polarized tunneling experiment using a superconductor/insulator/ferromagnet tunneling junction.

Microfabrication and magnetoelectric properties of amorphous magnetic-tunnel-junctions with Co–Fe–B/Al–O/Co–Fe–B hardcore structure

“…The value of effective spin-polarization of Co 60 Fe 20 B 20 at 4.2 K, P ¼ 58.1%, can be deduced from the Jullie`re's formula [11], due to which there is no contribution to TMR ratio from the amorphous Al-O band structure besides both Co 60 Fe 20 B 20 electrodes [12]. Such effective spin polarization in the amorphous alloy of Co 60 Fe 20 B 20 is higher than the experimental data of 50-52% for the Co 50 Fe 50 , Co 60 Fe 40 , and Co 84 Fe 16 alloys, measured at 0.2 K by Parkin et al [13], and Co 75 Fe 25 measured at 4.2 K by Han et al [5] Further more, low-junction resistance-area product RS of 4.6 kO mm 2 , small coercivity H C ¼ 25 Oe, and relatively large bias-voltage-at-half-maximum TMR with the value V 1/2 greater than 500 mV at RT had been achieved in such Co-Fe-B SBMTJs. Fig.…”

“…Although many investigations on new junction materials and structures for improving TMR ratio have been achieved in recent years [5][6][7][8][9][10], fabrication of good-quality polycrystal or amorphous MTJs is still a key challenge for the actual device applications with low cost.…”

High magnetoresistance in Co–Fe–B-based double barrier magnetic tunnel junction

“…1(b). The TMR ratio is up to 90.3% and 85% at 4.2 and 77 K, respectively, which is higher than that of 59.4% at RT due to the decrease of magnon and phonon excitations at 4.2 and 77 K [10]. Fig.…”

Electron spin resonance properties of semiconductor/granular film heterostructures with cobalt nanoparticles in millimeter waveband

“…The typical values of giant magnetoresistance at room temperature are within the range from 5% to 8%. (2) Magnetic tunnel junction structures consisting of metal ferromagnetic layers separated by an insulator layer [5][6][7][8][9][10]. The tunneling magnetoresistance ranges from 20% to 50% at room temperature.…”