Triple Magnetic Stacking in an Iron-Containing Cuprate with Cu–Fe–Cu Magnetic Blocks

The iron-substituted FeSr2YCu2O7.08 cuprate displays long-range magnetic ordering below TN ∼ 140 K, involving both Fe3+ cations in the charge reservoir block (CRB) and Cu2+ cations in the CuO2 planes. The magnetic structure comprises antiferromagnetic in-plane coupling within the FeO and the CuO2 layers, but a ferromagnetic coupling along the stacking direction. The low dimensional character of the magnetic structure is reflected in dynamic magnetic correlations over a wide range of temperature, Tonset = 400 K > T > TN = 140 K, as demonstrated by means of 57Fe-Mössbauer spectroscopy and muon spin relaxation spectroscopy measurements. The transition from confined low-dimensional magnetic correlations within each FeO and CuO2 layer to a three-dimensional magnetic structure by lowering the temperature is followed, emphasizing the role of the interlayer coupling. The observation of this new magnetic structure for a M-1212 type cuprate opens up new possibilities for exploring the interplay between magnetic and superconducting interactions in classical layered cuprates