Unusual impurity effects on the dielectric properties of CaCu 3-xMnxTi4O12

CaCu₃Ti₄O₁₂ has a large dielectric constant (ε∼10⁴ at 300 K), which is almost constant above 100 K, followed by a 100-fold reduction below 100 K. The physical mechanism of this anomalous behavior has been extensively investigated. We found that only 2% substitution of Mn for Cu dramatically quenches the huge ε of 10 ⁴ down to 100 over the measured temperature range from 4.2 to 300 K. In usual substitution effects, 2% impurity induces a tiny change in ε of the order of 2%. Thus the present substitution effect suggests that dipole moments cause fluctuating ferroelectric domains in CaCu₃Ti ₄O₁₂, as is similar to the frustrated dipole glass in LuFe₂O₄.