MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS X—ESR OF Gd IN Y-Ba-Cu-O BETWEEN ABOUT Tcand 600°C

Abstract

Temperature dependence of ESR linewidth, ΔHPP, of Gd3+ in Y1−xGdxBa2Cu3Oy (x=0.2, 0.5 and 1) has been studied between about Tc (zero-resistance temperature) and about 600°C. For all the samples, ΔHPP progressively broadens as temperature approaches Tc from high temperature side, presumably due to inhomogeneous magnetic field distributions arising from superconductivity. On the contrary, ΔHpp is nearly linear in temperature between about 100 K and 600 K with temperature gradient, ∂(ΔHPP)/∂T~0.6 G/deg. The linear temperature dependence is assumed to be due to the Korringa relation. From the temperature gradient obtained above, JN(EF) was estimated as 0.0025, where J is the coupling coefficient between Gd spin S and conduction carrier’s spin S, and N(EF) is the density of states on the Fermi surface. In addition, by substituting an appropriate value for J, N(EF) was crudely estimated for the Y-Gd-Ba-Cu-O system.