Giant current-direction dependence of anisotropic magnetoresistance and ultralow damping in single-crystal FeNi(001) alloy films

This work reveals a giant, current-direction-dependent anisotropic magnetoresistance (AMR) in single-crystal bcc FeNi alloys. The authors demonstrate that the AMR ratio for current along the [100] versus [110] crystal directions reaches a record 87 at 5 K. This effect exhibits a dramatic, nearly tenfold enhancement upon cooling---unlike the temperature-stable AMR observed in CoFe alloys. They further show that this material concurrently exhibits ultralow Gilbert damping (~2.3\ifmmode\times\else\texttimes\fi{}10${}^{\ensuremath{-}3}$) with negligible dependence on magnetization orientation. The unique combination of a giant, tunable magnetoresistance and low damping establishes bcc FeNi as a promising candidate for advanced magnetic memory and sensing technologies.