Measurement of the Zener Relaxation in High-Purity FeCr Single Crystals

Abstract

In binary alloys the measurement of the so-called Zener relaxation may be used as a non-destructive method to determine the activation enthalpy of self diffusion. High-purity FeCr single crystals with a Cr content of 53 at% were prepared by containerless inductive zone melting under Ar atmosphere. The internal friction was measured between temperatures of 300 to 1200 K using an inverted torsion pendulum in the frequency range between 2 and 80 Hz. A strong damping is observed below the Curie temperature of about 600 K due to domain wall motion. Above the ferromagnetic transition temperature a relaxation maximum occurs at about 920 K. The relaxation strength and the activation parameters were determined for single crystals with (100), (110) and (111) orientation. The relaxation can be assigned to the stress-induced reorientation of short-range ordered Fe and Cr atoms, respectively. An analysis yielded an effective activation enthalpy of (2.95 ± 0.3) eV showing no significant dependence on the crystal orientation. The orientation dependence of the relaxation strength and shear modulus indicates that jumps between nearest and next-nearest neighbor sites are involved. These results are compared with results of self-diffusion measurements.