EPR of Dy³⁺ in Copper Single Crystals

Abstract

The electron paramagnetic resonance (EPR) of rare-earth ions in noble metals has recently been the subject of an extensive study (see, for example, /l/). Most of the investigations were carried out on Er3+, Dy3+, Gd3+, and Yb3' ions in Ag and Au hosts. EPR in Cu was observed only on E r 3+ ions.In this paper we report what we believe to be the first observation of an EPR 3+ signal in a pure Cu sample doped with Dy ions. Using Cu of 99.996% purity a s starting material, a single crystal of dilute magnetic alloy was grown by the Bridgeman method. There arise considerable difficulties when determining small impurity concentrations in dilute metallic'alloys. The evaluation of the Dy concentration in our sample was carried out by comparison of the resonance signal intensities of Dy in Cu in accordance with their susceptibilities. Since the E r solubility in Cu i s known to be rather high / 2 , 3/, absolute measurements of i t s concentration are possible. The evaluation gave c(Dy) = 0.05 at%. EPR measurements were performed at Y = 9400 MHz in the temperature range 1.7 to 4.2 K. 3+ 3+ 'and E r Throughout the temperature range investigated an isotropic EPR signal was observed with a typical metallic line shape. Taking into account that r is the ground state of E r rare-eakh ions vary only slightly in the same metallic host, one may expect r to be the ground state also for Dy = 7.63 2 0.02 which i s reasonably close to the calculated value g = 7.55. At the lowest temperatures (T = 1.7 K), a hyperfine structure from the odd Dy isotopes has been observed (see Fig. 1). According to the Breit-Rabi expression, the hyperfine structure constant was determined giving A = (80 ? 3)-very close t o the respective value for the Dy163 isotope in the cubic crystal field in dielectrics. The temperature dependence of the EPR linewidth fitted well the formula AH = a + bT 7 3+ ions in Cu and assuming that the crystal field parameters for different 7 3+ ions in Cu. In fact, our measurements gave g =

Theory of crystal-field splitting and orbit-lattice coupling of rare-earth impurities in noble metals

“…However, the obtained constants W = 0.58 K, x = -0.4, are doubtful because, as they are transferred on the Dy3+ ion, they produce xDY = 0.64 with the Ts quartet in the ground state. At the same time, it is known [22] that the Dy3+ ground state in Cuis the r7 doublet. We have carried out a detailed analysis and found that only the OL coupling parameters and the A-value can be obtained from high-field magnetisation measurements with good accuracy.…”