Zero field magnetic phase transitions and anomalous low temperature upturn in resistivity of single crystalline alpha-TmAlB4

Abstract

In this study, pure alpha-TmAlB4 (YCrB4 structure) single crystals were grown with no beta-TmAlB4 (ThMoB4 structure) intergrowth, and zero magnetic field transitions were confirmed through specific heat capacity, magnetization, and electric resistivity measurements. The anomalous magnetic transition was found at approximately 6.2 K with long range antiferromagnetic transition at 5.6 K. The difference in field dependence between these two transitions indicates that they do not share a common magnetic origin. In addition, we investigated electrical resistivity down to 20 mK, and found upturn behavior at around 0.8 K. The low temperature upturn anomaly in resistivity was not found for other compounds of investigation for RAlB4 (R=rare earth elements), which suggests that an alpha-RAlB4 system has a significantly different ground state, compared to a beta-RAlB4 system. (C) 2010 American Institute of Physics. [doi:10.1063/1.3367975]