Theoretical interpretations of the angular dependence of the ESR resonance field of Dy in Pd

Abstract

The angular dependence of the observed resonance fields in the EPR spectrum of Dy in Pd is interpreted theoretically by taking the thermal average of the exchange interaction between Dy and the conduction electrons in the presence of an applied magnetic field as 〈 H〉=β[B 0+B 4O 4( L )+B 6O 6 ( L) ] S · H where B 0 is proportional to the effective isotropic exchange integral, and B 4 O 4( L) and B 6 O 6( L) represent orbital anisotropy in the exchange interaction. Mixing of the first excited multiplet (Γ 6 for x>0.16 or Γ (2) 8 for x<0.16) into the ground quartet is taken into account in computing the energy eigenvalues. By fitting the calculated transitions to the observed resonance fields, one can determine the exchange parameters and the crystal field parameters x and W . The best fit is obtained by using x=-0.422, W=-92 mK, B 0=-2.06 x10 −1, B 4=3.00 x10 −3 and B 6=-4.37 x10 ?−6. This demonstrates the necessity of introducing orbital anisotropy into the exchange interaction between Dy and the conduction electrons in Pd. The importance of anisotropic exchange to other properties of dilute magnetic alloys is discussed.