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RESEARCH PRODUCT

Critical Exponents and Randomness in SrTiO3 : Ca

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Since its discovery, the SrTiO3: Ca system is known to exhibit a number of features which were thought to arise from an impurity induced disorder. Non-linear dielectric measurements are used to obtain a more quantitative insight into this disorder. For 0.001 < xCa < 0.05, it is found that the non-linear susceptibility diverges at low temperatures. This is similar to what was previously reported in the dielectric random system KTaO3: Na. A method is proposed to quantify the contribution of the disorder to the non-linearities. It is found that the deviation from a true ferroelectric behaviour is not enough to call the low-temperature phase of SrTiO3: Ca a glass one. The maximum non-linearity observed for xCa = 0.003 and 0.004 decreases for higher xCa contents. It is shown that a simple model of temperature dependent dipole moment may account for both the linear and non-linear dielectric behaviour of SrTiO3: Ca.