Impact of hydrostatic pressure, nonstoichiometry, and doping on trimeron lattice excitations in magnetite during axis switching

Trimeron lattice excitations in single crystalline magnetite, in the form of c axis switching (i.e., the reorganization of the lattice caused by an external magnetic field) at temperatures below the Verwey temperature TV are observed by magnetization experiments. These excitations exhibit strong sensitivity to doping (with Zn, Al, and Ti), nonstoichiometry, and hydrostatic pressure (p < 1.2 GPa). The considered indicators of the axis switching (AS) are the switching field B-sw, the energy density needed to switch the axis E-sw, and the activation energy U. Our results show that hydrostatic pressure p weakens the low -T magnetite structure (decreases TV) and has roughly similar effects on AS in Zn-doped Fe3O4 and, to a much lesser extent, in stoichiometric magnetite. We have, however, found that while doping/nonstoichiometry also lowers TV, making it more prone to temperature chaos, it drastically increases the switching field, and activation and switching energies, suggesting that the trimeron order, subject to change while AS occurs, is more robust. Consequently, we conclude that the manipulation of trimerons in the process of axis switching and the mechanisms leading to the Verwey transition are distinct phenomena.