A MaxEnt-μSR study: Short-range ordering above the Verwey transition of Fe₃O₄

Using muon-spin rotation (μSR) the magnetic fields of Fe3O4 have been previously investigated. [1] The Verwey transition at Tv (~123 K) and a transition at Tw (~247 K) are observed. Using the sensitive Maximum-Entropy (MaxEnt) method, single-crystal-Fe3O4 μSR data are analyzed. [2,3] We review earlier results [3] and report the T-dependence of fields with Bext (720 Oe) // <110>. Below the demagnetization field, extra μSR signals are found at Bext // <110> indicating two frequencies at room temperature (RT) and two at 205 K. [3] At RT, the upper frequency follows the zero-field (ZF) trend seen in the Tv-Tw region of the ZF phase diagram. At 205 K, the lower frequency follows the extension of the ZF trend above Tw. These two ZF trends indicate short-range ordering related to electron conduction behavior and to precursor effects of the Tv transition. [1] Our MaxEnt-μSR finding is consistent with diffuse [4] & x-ray [5] scattering results above Tv. This interpretation shows two magnetizations, reflecting different short-range orders [3-5] in the ZF Mott-Wigner Fe3O4glass phase.

[1] C Boekema et al, Phys Rev B33 (1986) 2102 & references therein.

[2] C Boekema & MC Browne, AIP Conf Proc #1073 (2008) 260.

[3] C Morante & C Boekema, AIP Advances 10 (2020) 025005.

[4] A Bosak et al, Phys Rev X4 (2014) 011040.

[5] G Perversi et al, Nature Comm 10 (2019) 2857.