Abstract
AC susceptibility and muon spin relaxation data have been collected from a polycrystalline sample of LaSr2Cr2SbO9, a perovskite-like compound wherein the unequal distribution of Cr3+ and Sb5+ cations over two crystallographically-distinct six-coordinate B sites results in the onset of ferrimagnetism at ~150 K. The data are used to elucidate the dynamics of the ferrimagnetic domain walls, thought to lie in Sb-rich regions, and suggest an energy barrier of ~0.13 eV to their motion. The muon data confirm that the ferrimagnetic order is a true bulk phenomenon. The behaviour of this material is briefly compared to that of Ni2+- based relaxor ferromagnets.
Highlights
A simple cubic perovskite has the general formula ABO3 where A is usually a relatively large divalent or trivalent cation and B is a smaller transition-metal or p-block cation
When the experiments were repeated in an applied magnetic field, magnetic Bragg scattering consistent with Gz-type ferrimagnetic order was observed with the proportion of the sample undergoing ferrimagnetic order increasing as a function of applied field [5]
While we previously interpreted the frequency dependence of the AC susceptibility data as evidence for isolated spins decoupled from the main magnetically ordered phase, this more in-depth study shows that the lowfrequency dynamics are better associated with a domain wall effect, manifesting in a temperature-dependent relaxation time corresponding to a domain-wall barrier of ~0.13 eV and a spread of relaxation times which can be attributed to small variations in Sb concentration throughout the sample
Summary
A simple cubic perovskite has the general formula ABO3 where A is usually a relatively large divalent or trivalent cation and B is a smaller transition-metal or p-block cation. If the different species vary significantly in size and/or charge, they will have different coordination requirements and will occupy the six-coordinate sites in an ordered manner When such two species are present in a 1:1 ratio the compound is better formulated as a double perovskite, A2BB’O6. We found that LaSr2Cr2SbO9, unlike La3Ni2SbO9, exhibited clear magnetic Bragg scattering in powder neutron diffraction experiments conducted at 5 K in the absence of an applied field. This scattering could be attributed to long-range Gz-type ferrimagnetic order. The results are compared to those from related experiments conducted on analogous nickel-containing compositions
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