Precursor effects to the Verwey transition of Fe₃O₄: a MaxEnt-μSR study.

The magnetic fields of Fe₃O₄ have been previously studied using muon-spin rotation (μSR). [1,2] The Verwey transition at T_v(~123 K) and a transition at T_w(~247 K) are observed. Using Maximum Entropy (MaxEnt, ME) the single-crystal Fe₃O₄ μSR data are analyzed with improved precision. [3] Extra signals are found, indicating 2 signals at roomtemperature (RT) and 2 at 205 K. [4] These frequencies are found at B_ext // <110> and B_ext smaller than the demagnetization B. At RT, the upper signal follows the trend seen in the T_v-T_w region. At 205 K, the lower signal follows the extension above T_w. Short-range ordering could be interpreted as precursor effects to the T_v transition. [1,2] This short-range ordering relates to the “extra” 3d-electron (3d*) behavior. We re-examine the T dependence of fields with B (720 Oe) // <110>. Our Fe₃O₄ MEμSR study of the 3d* spin-phonon interaction could lead to a better understanding of the magnetism of this Mott-Wigner glass. [1] C Boekema et al, Hpf Interactions 31 (1986) 487; 17-19 (1984) 305. [2] C. Boekema et al, Phys Rev B33 (1986) 2102; Phys Rev B31 (1985) 1233. [3] C Boekema and MC Browne, MaxEnt 2008, AIP Conf Proc #1073 (2008) 260. [4] C Morante and C Boekema, MMM19 Las Vegas (2019) submitted.