ORTHORHOMBIC DISTORTIONS OF DY LU SUPERLATTICES/

Low-temperature X-ray measurements reveal that the spontaneous ferroma gnetic transition in a Dy/Lu superlattice is accomplished by the forma tion of orthorhombic domains. In contrast with bulk dysprosium, in whi ch the magnetoelastic distortion is discontinuous and area is not pres erved, this superlattice experiences a continuous distortion below the transition temperature which preserves the area of the unit cell in t he basal plane. The distortion is less than one-half that of single-cr ystal dysprosium. X-ray linewidths indicate the formation of columnar domains of common distortion whose extent along the c-axis at 20 K is comparable to the structural coherence at 300 K. The strain in the bas al plane is less than one lattice parameter per domain, demonstrating the importance of epitaxial clamping in this system. (C) 1998 Elsevier Science B.V. All rights reserved.