Low temperature dielectric and magnetic properties of Fe-ion-doped SrTiO3

Dielectric and magnetic properties of SrTi1−xFexO3 were measured for a single crystal sample (x=0.0032) and a ceramic sample (x=0.02). Temperature dependences of the dielectric constants were analyzed on the basis of a Vendik's formula, which describes a quantum paraelectric state accurately. A small amount of Fe impurities in the single crystal does not affect the characteristic temperatures of the dielectric properties, but does affect the quality of the crystal. This change in quality causes a large change in the dielectric constant of the quantum paraelectric state. The temperature dependence of the dielectric constant of the quantum paraelectric state of the ceramic sample is different from that of the single crystal not only quantitatively, but also qualitatively. The magnetic susceptibilities obey the typical Curie law, though a deviation of the Curie law was observed below 5 K for x=0.02. Crystals with the both concentrations remain in paramagnetic states at 2.5 K. The magnetic properties of SrTi1−xFexO3 can, in all likelihood, be explained by the orientation effect of free Fe3+ ions. In addition, an antiferroelectric interaction suggested for EuTiO3 by an analysis of dielectric constants based on a Barrett's formula was turned out to be unnecessary following analysis of the same data based on the Vendik's formula.