Abstract
Magnetic properties of multiferroic Eu1-xYxMnO3 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 TN = 47±0.5K for x = 0.2 and 45±0.5K for x = 0.3. Below TN 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 Eu1-xYxMnO3.
Highlights
Multiferroics are materials where long-range magnetic and polar order coexist with both order parameters being strongly coupled [1]
Since the paramagnetic spectra confirm a single interstitial muon stopping site, the two frequencies must arise from the field distribution of the long-range ordered (LRO) spin arrangement
Even for an induced field the size is low which indicates that the distortion of the Eu shell, i.e. the mixing of the non-magnetic ground state with magnetic higher crystalline electric field electronic states, is small and points to a weak Mn-Eu exchange coupling, estimated to be ∼0.5 K
Summary
Multiferroics are materials where long-range magnetic and polar order coexist with both order parameters being strongly coupled [1]. The perovskites Eu1−xYxMnO3 show multiferroicity without rare earth magnetism since Eu is in the non-magnetic 3+ state. Replacing Eu in part by Y changes the A-site volume (see Fig. 1-a) and with it the multiferroic properties, free from the additional influence of a magnetic rare earth moment. The present μSR studies investigate the pure volume effect on the magnetic properties of Mn3+ in Eu1−xYxMnO3.
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