UC Irvine

ESR measurements of the microwave absorption signal associated with weak ferromagnetism in single crystals of Eu2-xGdxCuO4 are presented for X band (9.5 GHz) and L band (1.2 GHz) as a function of the Gd concentration. The strong absorption observed at low magnetic fields was interpreted, for samples with low Gd concentration, as due to a field-induced spin reorientation transition occurring at a critical field Hc, coincident with the in-plane magnetic anisotropy effective field Heffy. For larger x the Cu-Gd magnetic interaction needs to be considered leading to smaller Hc values. Our measurements show that for Gd concentrations in the range 0≤x≤1 the experimental data can be very well fitted with parameters derived from previous measurements. This fact indicates that these compounds have nearly the same in-plane anisotropy effective field, in spite of the small changes in lattice parameters. For x=2 lattice distortions increase causing an Hc larger than the expected one. © 1996 American Institute of Physics.