Electron spin resonance of Gd in metallic Van-Vleck beryllides

The exchange parameters between Gd and the host magnetic ions in the Van Vleck beryllides PrBe13, EuBe13, TmBe13 and UBe13 were extracted using the electron spin resonance technique. A significant variation of the (positive) exchange across the rare-earth series was observed and was interpreted in terms of the dependence of the rare-earth-conduction electron exchange parameter on the 4f occupation number. (author)