Electron Spin Resonance and Nuclear Anisotropy in Dilute Alloys

Abstract

Electron spin resonance (ESR) of manganese in copper and silver metals was investigated with a special interest to an anomalous line shift observed in the so called antiferromagnetic region. The shift was found to be nearly inversely proportional to temperature. This fact gives rise to a possibility that the effective anisotropy may come from the nuclear spin polarization as was first observed in antiferromagnetic KMnF₃. To check this possibility, and ENDOR study of the Ag–Mn dilute alloys was done and the effect of the nuclear anisotropy was verified by the result that the ESR signal shows a slight shift when the nuclear spin system is under saturation with the frequency between 240 and 340 MHz. The hyperfine constant |A| was determined as 40×10⁻⁴ cm⁻¹ which agrees with the data given by the γ-ray polarization experiment below 1°K. It is also found that the shift is much enhanced under the presence of the third element, such as Fe, Co, Ni, and Pd atoms.