Properties of single RuO2 layer embedded in SrTiO3

A two-dimensional ferromagnet is an interesting system both for basic understanding of magnetism and for spintronic applications. However, making such a system is not easy as ferromagnetism becomes more and more unstable with reducing the thickness of a ferromagnet. For example, in oxide systems such as SrRuO
₃
, La
_1-x
Sr
_x
MnO
₃
, etc, ferromagnetism is lost around the thickness of a few unit cells [1, 2]. Recent theoretical studies have shown that a single SrRuO
₃
layer can exhibit half-metallicity when it is sandwiched between SrTiO
₃
lattices [3, 4]. The conduction electrons are predicted to exist only in RuO
₂
layers, which means that the system is a two-dimensional half-metal. In this work, in order to demonstrate the theoretical prediction, we have fabricated high-quality SrRuO
₃
/SrTiO
₃
superlattices using molecular beam epitaxy. Magnetic and transport measurements show a clear signature of ferromagnetism and conductivity.