Impurity-induced ferromagnetism and impurity states in Nd1/2Ca1/2(Mn0.95M0.05)O3

Impurity effects on the lattice structure and the electronic state are investigated for $B$-site substituted half-doped manganites ${\text{Nd}}_{1∕2}{\text{Ca}}_{1∕2}({\text{Mn}}_{0.95}{M}_{0.05}){\mathrm{O}}_{3}$ ($M$ is the $3d$ and $4d$ transition metals). We investigated the interrelation between the impurity-induced ferromagnetism and (1) the lattice structure (chemical pressure effect), (2) the magnitude of the impurity spin, and (3) the density of state (DOS) of the impurity $d$ state at the Fermi level ${E}_{\mathrm{F}}$. We found a strong correlation between the ferromagnetism and the DOS of the impurity state at ${E}_{\mathrm{F}}$, suggesting that the ferromagnetism can be ascribed to the enhanced one-electron bandwidth of the $\text{Mn}\phantom{\rule{0.3em}{0ex}}3d--M\phantom{\rule{0.3em}{0ex}}d$ hybridized band.