Speaker
Description
Using muon-spin rotation (μSR) [1] the magnetic fields of Fe3O4 have been previously investigated. The Verwey transition at Tv (~123 K) and a transition at Tw (~247 K) are observed. Using Maximum-Entropy (MaxEnt) μSR data of single-crystal Fe3O4 are analyzed with much improved precision. [2,3] We review earlier results [3] and report on our analysis of the temperature dependence of fields with B (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 trend seen in the Tv-Tw region of the zero-field (ZF) phase diagram. At 205 K, the lower frequency follows the extension of the ZF trend above Tw. These two ZF trends indicate plausible short-range ordering related to the “extra” 3d-electron conduction behavior. This should further be interpreted as precursor effects to the Tv transition. [1] Our MaxEnt-μSR finding is consistent with diffuse [4] & x-ray [5] scattering results above Tv providing a clear picture of the magnetic environments in Fe3O4. This new interpretation indicates two T-dependent magnetizations, reflecting different short-range orders [3-5] in the ZF phase diagram of this Mott-Wigner glass.[6]
Research supported by LANL-DOE, SJSU & AFC San Jose.
[1] C. Boekema et al, Phys Rev B33 (1986) 2102; Phys Rev B31 (1985) 1233 & references therein.
[2] C Boekema and MC Browne, MaxEnt 2008, AIP Conf Proc #1073 (2008) 260.
[3] C Morante and 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.
[6] JHVJ Brabers et al, J Physics Condensed Matter 12 (2000) 5437.
