A bottom spin-valve GMR sensor has been fabricated that has ultra-thin layers of high density and smoothness. In addition, these layers are inherently furnished with sub-monolayer thick oxygen surfactant layers. The sensor is fabricated using a method in which the layers are sputtered in a mixture of Ar and O2. A particularly novel feature of the method is the use of a sputtering chamber with an ultra-low base pressure and correspondingly ultra-low pressure mixtures of Ar and O2 sputtering gas (