Charge and spin states of Ru and Cu in magnetic superconductor ${RuSr}_{2} {GdCu}_{2} O_{8}$ studied by NMR

Authors:

Electronic and magnetic properties of

{RuSr}_{2} {GdCu}_{2} O_{8}

have been investigated by electric resistivity, magnetization, and Cu-, Ru-NMR measurements. Magnetic order

{(T}_{M} = 133 K)

and superconductivity

[T_{s} (onset) \sim 52 K]

have been confirmed. We observed two kinds of Ru-NMR signals (the hyperfine fields of

^{101} Ru

are 590 kOe and 290 kOe), suggesting a charge segregation of

{Ru}^{5 +} (S = 3 / 2)

and

{Ru}^{4 +} (S = 1)

in the

{RuO}_{2}

layers. The hyperfine field at the Cu site is diminishingly small, indicating magnetic interactions between

{CuO}_{2}

and

{RuO}_{2}

layers are weak. Assuming that holes are inherently doped in the

{CuO}_{2}

layers from the

({Ru}^{4 +},

{Ru}^{5 +}) O_{2}

layers, the high-

T_{c}

superconductivity can occur under weak magnetic interactions between Ru and Cu spins in

{RuSr}_{2} {GdCu}_{2} O_{8} .

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Charge and spin states of Ru and Cu in magnetic superconductorRuSr2GdCu2O8studied by NMR