X-ray absorption and X-ray magnetic circular dichroism studies of a monatomic bcc-Co(001) layer facing an amorphous Al-O tunnel barrier

Tunnel magnetoresistance (TMR) effect attracts much attention. Magnetic tunnel junctions (MTJs) with an amorphous Al-O tunnel barrier show large magnetoresistance ratio up to 70%. The orbital and spin moments of the 1 ML-Co(001) facing Al-O barrier, Al and Au metal layers were evaluated using X-ray magnetic circular dichroism (XMCD). X-ray absorption spectroscopy (XAS) was used to evaluate the oxidization state of the 1 ML-Co [001]. XAS and XMCD of the samples were measured from 635 to 855 eV. XAS data of the samples showed absence of oxidization in ML-Co layer. This indicates that the oxidization process of top Al layer was terminated without oxidizing the Co layer. The magnetic moments of 1 ML-Co was found larger than that of bulk Co indicating also that the Co layer adjacent to Al-O barrier is not oxidized.