Spin glass behavior in EuCu2Si2 single crystal grown by the flux method

Abstract

We grew single crystals of EuCu2Si2 by the Bridgman and In-flux methods, and studied their crystallographic and magnetic properties precisely to clarify the ground state at low temperatures. The Bridgman single crystals present almost the same magnetic properties as the previous arc-melted polycrystals, indicating a valence fluctuating state of the Eu ions. In the In-flux single crystals, the Eu ions are in the magnetic divalent state over the whole temperature range studied, and the system shows spin glass behavior below TSG = 11.5 K. From the crystallographic analyses, it is found that both the Bridgman and In-flux single crystals crystallize in the ThCr2Si2-type crystal structure, but in the In-flux crystals, a sizeable amount of Cu is replaced by Si, resulting in an off-stoichiometric composition. This replacement may cause the formation of random bonds for the magnetic exchange interactions, which leads to competing magnetic interactions and gives rise to spin glass features in the In-flux single crystals.