Magnetic ordering in Co78−xMnxB10Si12 amorphous alloys studied using X-ray magnetic circular dichroism

Using X-ray magnetic circular dichroism (XMCD), effective magnetic moments for Co and Mn in Co78−xMnxB10Si12 amorphous alloys were estimated in order to explain the different magnetic states found in the amorphous alloy depending on the Mn content. As the Mn content was increased, the Co-Mn amorphous alloy changed from a ferromagnet to a paramagnet and then to a mictomagnetic state (x = 30 at%) at room temperature. When x > 25 at%, a reentrant spin glass behavior was also observed below 50 K. XMCD analysis showed that the magnetic moments for both Co and Mn were severely reduced by the structural disorder. It was also found that the Mn-Mn pair exchange interaction was ferromagnetic, regardless of the composition (up to 30 at%); hence, antiferromagnetic JCoMn exchange interaction is believed to be responsible for the reentrant spin glass behavior as well as the mictomagnetic state observed for the alloys with high Mn content.