Measurements of magnetostriction constants of epitaxial garnet films by double-crystal x-ray diffraction

Magnetostriction constants lambda111 have been determined at room temperature with the double-crystal x-ray diffraction technique by measuring a small change in the lattice parameter. Measurements were carried out for epitaxial garnet films of Y3Fe5O12 and Sm/sub 0.85/Tm/sub 2.15/Fe5O12 grown on [111] oriented Gd3Ga5O12 substrates; and also for flux-grown bulk single crystal of Y3Fe5O12. Values of lambda111 obtained were -1.7 x 10-6 for film and -3.0 x 10-6 for bulk crystal. lambda111 of Sm/sub 0.85/Tm/sub 2.15/Fe5O12 was -5.0 x 10-6. The discrepancy in lambda111 values between film and bulk Y3Fe5O12 is almost accounted for by the fact that the film can deform only perpendicular to the film plane due to the shear force of the substrate. It has been experimentally demonstrated that lambda111 does not depend on film thickness or lattice mismatch, which is consistent with the present analysis