Magnetic properties of the multiferroic compounds Eu_1-xY_xMnO₃ (x = 0.2 and 0.3)

Magnetic properties of multiferroic Eu_1-xY_xMnO₃ with x = 0.2, 0.3 were studied by μSR and Mossbauer spectroscopy. Both compounds are known to become antiferromagnetic with Mn³⁺ being the only magnetic ion. We find T_N = 47±0.5K for x = 0.2 and 45±0.5K for x = 0.3. Below T_N three different magnetic states (AFM-1, AFM-2, AFM-3) are formed. The μSR parameters of the uppermost magnetic state (AFM-1) are alike in both compounds, and compatible with a commensurate modulated collinear spin structure. The magnetic ground state in x = 0.2 (AFM-3) is shown to be single phase. Its spectral parameters support the proposal of a cone-like spin structure, yet with incommensurate modulation. The ground state for x = 0.3 is found to have an incommensurate spiral spin structure. ¹⁵¹Eu Mössbauer spectroscopy measured the Eu hyperfine field induced by the Mn³+ ions. Its low value (∼4T) means that mixing with higher Eu electronic states is small and that the Mn-Eu exchange coupling is weak (∼0.5K). The various magnetic transitions appear as small irregularities in the temperature dependence of the hyperfine fields. The present results are discussed in terms of different published magnetic phase diagrams of Eu_1-xY_xMnO₃