Magnetoelastic coupling in RuSr2GdCu2O8

Abstract The complex Young's modulus, E , of RuSr 2 GdCu 2 O 8 was measured for the first time in the temperature range from 1.5 up to 900 K . In the paramagnetic phase the real part of the Young's modulus decreases almost linearly with T , in agreement with the usual quasiharmonic approximation of the lattice dynamics described by the Debye model. A Debye temperature of about 390 K well reproduces the experimental data, in agreement with θ D obtained by means of specific heat measurements performed by other authors. However, around the ferromagnetic transition the real part of E is affected by the onset of the magnetic order, slightly decreasing from the expected Debye behavior down to about 90 K , evidencing a magnetoelastic coupling in RuSr 2 GdCu 2 O 8 . On further cooling, E ′ increases, becoming greater than the value expected from the Debye model.