Tensor components, ferroelectrics

No anomalies in the dielectric properties appear in the direction perpendicular to the spontaneous polarization in single-axial ferroelectric crystals (Rochelle Salt, TGS, KH2PO4 and matty others), where otdy one direction of spontaneous polarization exists. In snch cases, we could describe the dielectric properties only in this direction, i.e. in one-dimensional coordinate system. We could therefore omit tensor indexes for the tensor components. 

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