Structural transformation and magnetic properties of Sr-doped Gd 2CuO 4

Abstract

X-ray diffraction and magnetic susceptibility measurements have been investigated for the effects of Sr doping on the structural and magnetic properties of T′-phase compound Gd 2CuO 4. For (Gd 1- x Sr x ) 2CuO 4, the T' phase is retained in the range 0≤ x≤0.05 and transforms into T ∗ phase at about x = 0.4, in which the local CuO units are a square and a pyramid, respectively. The magnetic ordering temperatures T N( Cu) ∼ 285 K determined from the temperature dependence of magnetic susceptibility are not sensitive to the Sr doping for x ≤ 0.3, indicating that extra holes cannot be doped onto the CuO plane. The anomaly of the magnetic susceptibility observed at T m ∼ 20 K is suppressed with Sr doping, while the temperature T m is almost unchanged. Thus, this magnetic anomaly is thought to be closely related to the ionic size of doping cations. The similarities and differences for structural and magnetic properties of (Gd 1- x Sr x ) 2CuO 4 and (Gd 2- x Ce x CuO 4 are discussed.