Investigation of the local Fe magnetic moments at the grain boundaries of the Ca_2FeReO_6 double perovskite

摘要

The local Fe ferromagnetic (FM) moment at the grain boundaries of a ceramic sample of Ca_2FeReO_6 double perovskite was investigated by means of x-ray magnetic circular dichroism spectroscopy at the Fe L_(2,3) edges and compared to the overall bulk magnetization. We found that, at the grain boundaries, the Fe FM moments at H=5 T are much smaller than expected and that the MXH curve is harder than in the bulk magnetization. These results suggest a larger degree of Fe/Re antisite disorder at the grain boundaries of this sample, shedding light into the intriguing nonmetallic resistivity behavior despite the reported presence of free carriers.