Berlin 2005 – scientific programme
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MA: Magnetismus
MA 13: Spinabh
ängiger Transport I
MA 13.6: Talk
Saturday, March 5, 2005, 12:00–12:15, TU EMH225
Interfacial coherence and sign of spin polarization — •Andy Thomas1, Biswarup Satpati2, and Jagadeesh Moodera1 — 1Francis Bitter Magnet Lab., MIT, Cambridge, USA — 2Institute of physics, Bhubaneswar, India
The inverse TMR in magnetic tunnel junction La0.7Sr0.3MnO3/ SrTiO3(STO)/ Co structures investigated by DeTeresa et. al. was explained by the influence of interface bonding between the Co and the STO barrier. The d-band matching caused the d-electrons to tunnel predominantly and hence the sign of spin polarization P was negative [1].
Our recent results disagree with this general conclusion. Direct measurements of P in FM/STO/Al structures using the Meservey-Tedrow technique (SPT) gave values of P to be +31 % for Co, and +29 % (+10 %) for Fe (Ni) respectively. These values agree fairly well with values found for Al2O3 already 30 years ago, and thus the theoretical explanation of the d-band match in these structures is not generally valid and has to take additional parameters into account (e.g. [2]).
To look further into the coherence of the interface structure and the sign of spin polarization, the interfaces are investigated with HR-TEM and compared to the TEM images of [3]. Factors that determine the sign of P are discussed to give input for a more complete theoretical explanation.
Supported by NSF and Humboldt Foundation funds. [1] DeTeresa et. al., PRL 82, 4288 (1999), [2] Oleinik et. al., PRB 65, 020401 (2001), [3] Pailloux et. al., PRB 66, 014417 (2002)