Spin-phonon coupling in PrMn₂O₅ nanorods

PrMn₂O₅ nanorods with five axial (LC) × radial lengths of 63 nm × 25 nm, 150 nm × 25 nm, 152 nm × 29 nm, 259 nm × 86 nm, and 262 nm × 87 nm were fabricated by the hydrothermal method. Experiments on magnetic susceptibility demonstrate incommensurate antiferromagnetic (ICAFM) (T_N) and ICAFM-to-commensurate antiferromagnetic (T_N′) ordering at 43 and 20 K, respectively, in the samples with LC ≤ 259 nm. At LC = 262 nm, both T_N and T_N are shifted to higher temperatures and the samples exhibit magnetic correlation from 150 K. Experimentally obtained M-H curves demonstrate that only the sample with LC = 262 nm exhibits a hysteresis loop. Raman spectra obtained at various temperatures reveal that in only the sample with LC = 262 nm does the A_g + B_1g mode exhibit a large Raman shift until the sample is cooled to 150 K. The distinctiveness of the LC = 262 nm sample arises from annealing. This treatment reduces the barrier to magnetic ordering that is caused by defects and promotes spin-phonon coupling at high temperatures.