Cr5+ in KH2AsO4: A Halperin-Varma-type center

Abstract

The electronic wave function of Cr5+ (3d1) in KH2AsO4 and KH2PO4 is identified as dx2 - y2. Its symmetry property in the hydrogen-bonded tetrahedron allows a rotational motion of dx2-y2 c which breaks the symmetry in the Halperin-Varma sense. We show that its local coupled relaxation time is one order of magnitude longer than the slow ferroelectric cluster dynamics which can be identified with the same center independently and that the motion perpendicular to the c axis must be the cause. © 1976 The American Physical Society.