Spin-phonon study of EuMn₂O₅ nanorods

EuMn₂O₅ multiferroic nanorods, with diameters radial × (〈L_C〉) lengths of 25(6) nm × 47(15) nm and 51(16) nm × 70(26) nm, were fabricated by the hydrothermal method. Ferrimagnetic ordering below 50 K (T∗) is observed in the 〈L_C〉 = 70 nm sample, which exhibited ferromagnetic (FM) behavior below T∗ in a field cooling process. No similar behavior was found in the 〈L_C〉 = 47 nm sample. These observations reveal that only the 〈L_C〉 = 70 nm sample has a meta-FM state, and this sample exhibits the stronger coupling between the Mn ions. Raman spectra of both sets of samples were obtained in 0, 610, 1000, 1600, and 2000 G magnetic fields. The red-shift of the A_g (681 cm^-1) mode of the both samples increased with the strength of the field above 1000 G, indicating the existence of spin-phonon interaction. The smaller sampled exhibited a larger red-shift, suggesting that the size importantly affects the of EuMn₂O₅ nanorods.