Effect of Uniaxial Stress on the EPR Spectra of the Er³⁺ Ions in Cu

Abstract

The data on spin-phonon coupling (SPC) of localized magnetic states may be informative when treating a microscopic model of the crystalline field in metals.F o r dielectrics such information is usually obtained when studying the effect of an externally applied uniaxial s t r e s s on the E P R spectra /l/. In recent experiments on thin metallic films /2 to 4/ the SPC constants have been determined; however, these constants may appear to be s m a l l e r than they actually a r e due to the lack of deformation control of the sample. Up to now the possibility of performing such measurements on bulk metallic samples has seemed to b e rather doubtful due to plastic deformation effects, but our experiments provide evidence that these studies a r e not only possible but also very informative.We have chosen for the experiments a copper single crystal containing 0.04 at% E r . The [liO] direction of the sample approximately coincided with the tensile load axis and was perpendicular to the rotation plane of the external magnetic field. E P R measurements were carried out at = 9400 MHz and T = = 1 . 8 K. In an unloaded sample was observed an isotropic line from the E r ion with g-factor g = 6.810 + 0.005 and linewidth AH = (16 + 0.8)G. The gfactor shows that the ground state for Cu:Er is the doublet r,. Application of load to the sample altered the E P R spectrum in such a way that when rotating the sample the linewidth remained unchanged, while in the g-factor behaviour there a r o s e an anisotropy ( F i g . 1) which increased with load up to 1 . 2 kg/mm . The g-factor anisotropy observed may be well described by the empirical expression 3+ 0 --2 (1 1 2g = g + A + B c o s @ , 0 where 8 is the angle between the [ l l O ] direction and the orientation of the external magnetic field. The analysis of these experimental data leads to the con-1 ) Kazan 420029, USSR.