Spin, charge and lattice dynamics of magnetization processes in frustrated Shastry-Sutherland system TmB4

TmB4 - the metallic tetraboride with a geometrically frustrated Shastry-Sutherland lattice (SSL) has attracted recently a lot of attention. It exhibits a strong Ising-like anisotropy along the c-axis and a rather complex phase diagram of the ordered magnetic phase below TN ≈ 11.7 K in which besides the main magnetization (M) plateau also small fractional plateaus can be observed. To learn more about the properties of fractional plateaus we have investigated the dynamics of magnetization processes in TmB4 by M vs. H (applied magnetic field) measurements at different temperatures and different field sweep rates (swr) 1.8 K. In addition, experiments of the charge carrier mobility and magnetostriction as a function of temperature and magnetic field were carried out to specify the interplay between magnetic structure and the charge dynamics, and the role of the magneto-elastic interaction in this compound, respectively. It was shown that the magnetization values of fractional plateaus become elevated with the increase of temperature at which magnetization takes place and with the decrease of magnetic field sweep rate, which points to inconsistency with theoretical predictions based on Glauber dynamics. Moreover, it turned out that the transitions between magnetic phases during magnetization processes are accompanied by an anomalous behavior of charge mobility and distinctive variations of magnetostriction.