The exceedingly strong two-dimensional ferromagnetism in biatomic layer SrRuO_(3)with a critical conduction transition

In recent years,few-layer or even monolayer ferromagnetic materials have drawn a great deal of attention due to the promising integration of two-dimensional(2D)magnets into next-generation spintronic devices.The SrRuO_(3)monolayer is a rare example of stable 2D magnetism under ambient conditions,but only weak ferromagnetism or antiferromagnetism has been found.The biatomic layer SrRuO_(3)as another environmentally inert 2D magnetic system has been paid less attention heretofore.Here we study both the bi-atomic layer and monolayer SrRuO_(3)in(SrRuO_(3))n/(SrTiO_(3))m(n=1,2)superlattices in which the SrTiO3 serves as a non-magnetic and insulating space layer.Although the monolayer exhibits arguably weak ferromagnetism,we find that the bi-atomic layer exhibits exceedingly strong ferromagnetism with a Tc of 125 K and a saturation magnetization of 1.2μB/Ru,demonstrated by both superconducting quantum interference device(SQUID)magnetometry and element-specific X-ray circular dichroism.Moreover,in the bi-atomic layer SrRuO_(3),we demonstrate that random fluctuations and orbital reconstructions inevitably occurring in the 2D limit are critical to the electrical transport,but are much less critical to the ferromagnetism.Our study demonstrates that the bi-atomic layer SrRuO_(3)is an exceedingly strong 2D ferromagnetic oxide which has great potentials for applications of ultracompact spintronic devices.