Competing magnetic interactions in (Dy 0.375 Y 0.625 ) 2 Cu 2 O 5 solid solution studied by EPR

(Dy 0.375 Y 0.625 ) 2 Cu 2 O 5 is an antiferromagnet below T N = 11 K, displaying many signs of low‐dimensional magnetism. Electron paramagnetic resonance (EPR) investigation of different magnetic interactions in (Dy 0.375 Y 0.625 ) 2 Cu 2 O 5 solid solution is carried out by analysis of thermal evolution of EPR spectral parameters (integrated intensity, effective resonance field, effective linewidth) evaluated in the paramagnetic phase. A model, proposed earlier to explain metamagnetic transitions in the anntiferromagnetic phase was used to interpret the observed magnetic behaviour. Manifestations of copper chains existing in the (Dy 0.375 Y 0.625 ) 2 Cu 2 O 5 structure has been found in the EPR spectrum and the values of appropriate exchange constants connected with a hierarchy of exchange interactions has been calculated. At about 40 K a dimensional crossover from 2D to 3D behaviour has been observed in the temperature dependence of the product of the EPR integrated intensity and temperature. At high temperatures ( T > 200 K) the EPR spectrum is suggestive of the presence of defect centres consisting of antferromagnetically coupled copper spins, forming dimers with the S = 0 ground state. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)