Magnetisation and ESR Studies of Gd(Ni_1−xRh_x)₅ Compounds

Magnetisation and electron spin resonance measurements are performed on Gd(Ni_1−xRh_x)₅ compounds with x = 0, 0.1, 0.2, 0.3, 0.5, and 1.0. In the ordered state the value of the spontaneous moments is 6.5 μ_B/f.u. in GdNi₅, rising to 6.7 μ_B/f.u. at the GdRh₅ end of the series. Both θ_p and T_c show rapid variation with Rh substitution, particularly at the GdNi₅ end of the series where dθ_p/dc ≈ 1.1 K/at% Rh. The ESR measurements indicate that the system is bottlenecked. The substitution of Rh for Ni reduces the slope of the linewidth from 7 × 10⁻⁴T/K in GdNi₅ to 4 × 10⁻⁴T/K in GdRh₅ and raises the g‐value from 1.923 in GdNi₅ to about 2.000 at the GdRh₅ end of the series; both indicative of a change in the character of the conduction electrons from predominantly d‐like in GdNi₅ to predominantly s‐like in GdRh₅. From the g‐shift a value of J = −0.005 eV is obtained for the effective exchange integral. Both, ESR and magnetic data indicate that the density of d‐states goes through a minimum close to the GdNi₅ end of the series.