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A Magnetoresistance Induced by a Nonzero Berry Phase in GeTe/Sb 2 Te 3 Chalcogenide Superlattices
Author(s) -
Tominaga Junji,
Saito Yuta,
Mitrofanov Kirill,
Inoue Nobuki,
Fons Paul,
Kolobov Alexander V.,
Nakamura Hisao,
Miyata Noriyuki
Publication year - 2017
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201702243
Subject(s) - materials science , magnetoresistance , chalcogenide , superlattice , condensed matter physics , phase (matter) , geometric phase , alloy , magnetic field , impurity , polar , optoelectronics , composite material , physics , quantum mechanics , astronomy
The chalcogenide alloy Ge–Sb–Te (GST) has not only been used in rewritable digital versatile discs, but also in nonvolatile electrical phase change memory as a key recording material. Although GST has been believed for a long time not to show magnetic properties unless doped with magnetic impurities, it has recently been reported that superlattices (SLs) with the structure [(GeTe) L (Sb 2 Te 3 ) M ] N (where L , M , and N are usually integers) have a large magnetoresistance at room temperature for particular combinations of L and M . Here it is reported that when [(GeTe) L (Sb 2 Te 3 ) M ] N chalcogenide SL films are thermally annealed at 470 K and cooled down to room temperature under an external magnetic field accompanied by current pulse injections, a large magnetoresistance change (>2500 Ω) is induced. This study shows that the phenomenon has a strong correlation with the GeTe thickness and the periodic structure of the SL films, and that it is induced by the structural phase transition between electrically nonpolar and polar phases in the GeTe layers in the SLs. This study proposes that the relationship between the polar (ferroelectric) phase and the Berry curvature in the SLs is responsible for the magnetoresistance change.