High frequency (208 GHz) determination of the cubic spin Zeeman term for the U~(3+) ion in the dilute magnetic semiconductor crystals of Pb_(1-c)U_xTe and Pb_(1-x)U_xSe at 5 K by electron paramagnetic resonance

摘要

A high-frequency (208 GHz) Electron Paramagnetic Resonance (EPR) study on the U~(3+) ion (5f~3, ~4I_(9/2), S=3/2) embedded with 3% concentration in the dilute magnetic semiconductor crystals of PbTe and PbSe, each characterized by cubic symmetry, has been performed at ～5 K, especially in view to determine the value of the Zeeman cubic spin term parameter u, and the site symmetry of the U~(3+) ion (radius 0.089 nm), substituting for the Pb~(2+) ion (radius 0.119 nm). The experimental spectra reveal the presence of only one set of EPR lines from U~(3+) ions in these host crystals, exhibiting cubic symmetry, whose magnetic axes are oriented along the crystal axes. The spin-Hamiltonian parameters are for both crystals: g= 1.9811, u=-0.0257.