Magnetic Chiral Dichroism Studies using Energy Filtered Images

Abstract

Magnetic thin films of Co₈₀Cr₁₆Ta₄ were sputtered onto identical CrMo seed-layers at -200 V bias and 3 different substrate temperatures (150, 200, and 250°C). Energy-filtered transmission electron microscopy (EFTEM) was performed to analyze Cr levels at the grain boundaries as well as inside the grains. These quantitative Cr measurements were used to estimate the local values of magnetocrystalline anisotropy (K_u) and, together with grain size distributions, calculate the product of K_u and the grain volume (K_uV), a quantity which is a measure of thermal stability. The results show that the coercivity as well as the percentage of stable grains increased with increasing substrate temperature. The increase in the number of stable grains is produced by the enhancement in the K_u value from Cr depletion of the grain interiors and the magnetic decoupling between the grains from Cr grain boundary segregation.