Crystal structure, oxidation state and magnetism of SrxLa2−xCu0.5Ru0.5O4 (x=1, 1.5)

• SrLaCu0.5Ru0.5O4 (I) larger Jahn–Teller (J–T) distortion than Sr1.5La0.5Cu0.5Ru0.5O4 (II).
• Octahedral Cu/RuO6 units are more elongated in I than in II.
• Mixed ion pairs Ru5+/Ru4+↔Cu+/Cu2+ are present in I, while Ru remains as Ru5+ and Cu as Cu2+ in II.
• Negative Weiss temperature of I significantly lower, consistent with higher J–T distortion.

SrxLa2−xCu0.5Ru0.5O4 (x=1, 1.5) oxides with K2NiF4-type structure were prepared by solid state reaction and characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, magnetic and electrical resistivity measurements. The SrLaCu0.5Ru0.5O4 phase was obtained for the first time with a negligible amount of impurities. The octahedral Cu/RuO6 units are more elongated in SrLaCu0.5Ru0.5O4 than in Sr1.5La0.5Cu0.5Ru0.5O4 indicating a greater extent of static Jahn–Teller distortion. XPS suggests that mixed ion pairs Ru5+/Ru4+↔Cu+/Cu2+ are present in SrLaCu0.5Ru0.5O4, while Ru remains as Ru5+ and Cu as Cu2+ in Sr1.5La0.5Cu0.5Ru0.5O4. Both samples show spin-glass behavior, which can be explained by competition between ferromagnetic and antiferromagnetic superexchange interactions. The negative Weiss temperature estimated for SrLaCu0.5Ru0.5O4, −318 K, is significantly lower than −11.5 K deduced for Sr1.5La0.5Cu0.5Ru0.5O4 which may be related to the higher static Jahn–Teller distortion in the former oxide.

SrLaCu0.5Ru0.5O4 with K2NiF4-type structure show a larger static Jahn–Teller distortion than Sr1.5La0.5Cu0.5Ru0.5O4, which may be related to stronger antiferromagnetic superexchange interactions. Figure optionsDownload as PowerPoint slide