Unusual magnetic properties and time dependent magnetization in ErCo3Ga2 (abstract)

Abstract

In this abstract we will present the measurements of magnetization, ac susceptibility, and the time dependent effects on the magnetization of polycrystalline samples of ErCo3Ga2 and YCo3Ga2. The field cooled (FC) and zero field cooled (ZFC) magnetization data suggest a spin glass transition in YCo3Ga2 below 160 K. The FC magnetization ErCo3Ga2 exhibits a negative minimum at 25 K and a compensation temperature at 150 K. It is suggested that ErCo3Ga2 has two magnetic phase transitions: one at 150 K (most likely a spin glass transition due to Co sublattice) and the other below 25 K (due to Er sublattice ordering). We have found an unusual time dependence of magnetization of ErCo3Ga2 at a constant temperature (below 150 K) and constant applied magnetic field. The magnetization M increases with time t and dose not attain a constant value over a period of 64 h. The time dependence of magnetization follows the relation MT,H(t)=MT,H(t0)+aT,H ln t. The slope aT,H is always positive and depends on temperature and the applied magnetic field. The field dependence of the slope shows a peak at a field Ha. The value of Ha decreases with increasing temperature. At a constant temperature the slope aT,H increases exponentially with the applied magnetic field and then decays towards zero values at high applied magnetic field. This suggests an activation energy process. Detailed experimental results on time effects will be presented.