Critical composition of La0.7-xDyxCa0.3Mn(Fe)O3La0.7-xDyxCa0.3Mn(Fe)O3 for high CMR

La0.7-xDyxCa0.3Mn(Fe)O3La0.7-xDyxCa0.3Mn(Fe)O3 is studied extensively using Mössbauer spectroscopy, AC susceptibility, DC magnetization, and resistivity measurements. MR shows a cusp-like increase at the critical composition x=0.10x=0.10. Based on the experimental results, we provide an explanation for the high MR. Several properties of the manganite that undergo changes at this composition as xx is varied are found. Our study, thus, reveals a mechanism by which CMR in excess of 108%108% can be obtained.