Spin-flop magnetoresistance in Gd/Co multilayers

Low-temperature magnetotransport and magnetization measurements have been p erformed at high magnetic fields in samples of a layered artificial ferrima gnet: multilayers made by sequential sputtering of Gd and Co. Strong interf acial reaction leads to severe alloying and, if the Co layer is nominally t hick enough (greater than or equal to 4 nm), the samples are mainly compris ed of alternated pure Co and Gd0.7Co0.3 alloy layers. Such spin systems are antiferromagnetically coupled at the interface region, and the compensatio n temperature of this "giant" ferrimagnet is determined by the thickness of Gd and Co layers. Both magnetization and magnetoresistance measurements in dicate the so-called spin-flop transition at temperatures below the Curie p oint of the alloy layer (similar to 189 K). Spin-flop magnetoresistance res embles the anisotropic magnetoresistance of ferromagnets except for the fie ld range in which it develops: H>10(3)-10(4) Oe for modulation length of si milar to 15 nm. The effect arises in the Co layers from anisotropic carrier scattering. [S0163-1829(99)07633-X].