Apparent spin polarization decay in Cu-dusted Co/Al2O3/Co tunnel junctions

Area of Science:

• Materials Science
• Condensed Matter Physics
• Spintronics

Background:

• Magnetic tunnel junctions (MTJs) are crucial for spintronic devices.
• Interfacial layers can significantly alter MTJ performance.
• Previous studies showed conflicting results regarding copper interlayers in MTJs.

Purpose of the Study:

• To investigate the impact of interfacial copper (Cu) layers on Co/Al2O3/Co magnetic tunnel junctions.
• To clarify the reasons behind differing magnetotransport behaviors reported in the literature.
• To understand the relationship between Cu growth morphology and device properties.

Main Methods:

• In situ growth characterization techniques were employed.
• Ex situ magnetotransport measurements were performed.
• Analysis of tunneling magnetoresistance (TMR) decay lengths and spin polarization.

Main Results:

• Cu interlayers grown on Cobalt (Co) exhibited an exponential decay of TMR with a decay length (ξ) of approximately 0.26 nm.
• Cu interlayers grown on Aluminum Oxide (Al2O3) showed a longer decay length of approximately 0.70 nm.
• Tunneling spin polarization was suppressed by at least a factor of 2 for monolayer Cu coverage and became negligible beyond approximately 5 ML.

Conclusions:

• The observed differences in decay lengths are attributed to distinct growth morphologies of Cu on Co versus Al2O3.
• This study resolves a discrepancy in the existing literature regarding the role of Cu interlayers.
• The findings highlight the critical influence of interfacial engineering on spintronic device performance.