Low temperature magnetic and transport properties of the sol-gel derived Cd doped ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{Mn}}_{1-x}{\mathrm{Cd}}_x{\mathrm{O}}_3(0⩽x⩽0.20)$ manganite system show ferromagnetism and cluster spin-glass behavior. Metal-insulator transition (MIT) is exhibited only by the samples with $x⩽0.1$; and for higher concentrations ($x=0.15$ and 0.20), samples are semiconductors. The MIT shifts to the lower temperature regime with increasing Cd content, indicating an increase of disorder in the system. Structural analysis shows local strain-induced small lattice distortion of the $\mathrm{Mn}{\mathrm{O}}_6$ octahedra with Cd doping. With increasing Cd content, the system undergoes interesting paramagnetic to ferromagnetic (with $x<0.10$) as well as paramagnetic to cluster spin-glass (for $x⩾0.10$) transitions. ac susceptibility $\left({\chi }_{\mathrm{ac}}\right)$ and magnetic relaxation measurements confirm this cluster spin-glass behavior. ${\chi }_{\mathrm{ac}}$ is found to follow the critical slowing down law $(\tau ∕{\tau }_0={\epsilon }^{-z\nu })$. The magnetic hysteresis loops indicate a field-induced irreversible ferromagnetic phase due to the presence of “weak” antiferromagnetic domains in the samples with $x⩾0.10$. This typical behavior is found to be most prominent in the sample with $x=0.15$. The observed cluster spin-glass state is explained by considering the interactions between the ferromagnetic and antiferromagnetic clusters in these doped systems having disorder and reduced geometrical tolerance factor $t$, which resulted from the random substitution of Mn with Cd ions.

• Received 17 January 2006

DOI:https://doi.org/10.1103/PhysRevB.74.104407