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Unravelled and Glassy Magnetism in PbFe1/2Nb1/2O3 - (2) Neutron Scattering



C. Stock, B. Roessli, Peter M. Gehring, Jose Rodriguez Rivera, N. Giles-Donovan, S. Cochran, Guangyong Xu, P. Manuel, M. J. Gutmann, William D. Ratcliff, T. Fennell, Y. Su, X. Li, H. Luo


We apply neutron scattering to investigate the magnetism in the relaxor ferroelectric PbFe1/2Nb1/2O3 (PFN). Similar to the lack of spatially long-range ferroelectric order in prototypical relaxors like Pb(Mg,Zn)1/3Nb2/3O3 (PMN and PZN), spatially long-range magnetic order, in our single crystal of PFN, is not observable at any temperature. This differs from smaller samples and we discuss this discrepancy in the companion paper analyzing depth dependent muon spectroscopy. Our neutron scattering measurements find spatially short-range antiferromagnetism is onset over a broad range of temperatures and defined by a band of slow frequencies. Polarized neutron measurements show that the average bulk magnetic moment direction is isotropic, lacking any preferred direction. However, on decreasing temperature the magnetism crosses over to a region where magnetic spatial correlations gradually become more disordered on cooling. Based on analogues with disordered ferromagnets, we suggest that this is a crossover from a paramagnetic to a glass phase. Through investigating the low-energy acoustic phonons we find evidence of multiple distinct structural regions generating a significant amount of local disorder. We propose that, similar to the structural properties of relaxors PMN and PZN, low temperature magnetism in PFN is unravelled by random fields.
Physical Review B


neutron, glassy, magnetism


Stock, C. , Roessli, B. , Gehring, P. , Rodriguez Rivera, J. , Giles-Donovan, N. , Cochran, S. , Xu, G. , Manuel, P. , Gutmann, M. , Ratcliff, W. , Fennell, T. , Su, Y. , Li, X. and Luo, H. (2022), Unravelled and Glassy Magnetism in PbFe<sub>1/2</sub>Nb<sub>1/2</sub>O<sub>3</sub> - (2) Neutron Scattering, Physical Review B (Accessed March 1, 2024)
Created October 10, 2022, Updated November 29, 2022