⁶³Cu NMR and Susceptibility Studies of YbCu₂Si₂ Single Crystal

Abstract

The temperature dependences of susceptibility and ⁶³Cu Knight shift in YbCu₂Si₂ single crystal have been measured for the fields parallel and perpendicular to the c-axis in the temperature range between 4.2 K and 300 K. The anisotropy of the susceptibility was found to be quite increased with decreasing temperature between 20 K and 200 K, suggesting that the crystalline electric field (CEF) effect is important in YbCu₂Si₂. It was also observed that the linear relation between the Knight shift and the susceptibility is broken around 100 K for both the directions, and that the hyperfine coupling is highly anisotropic even at higher temperatures. The origins of the non-linearity and the anisotropy of the hyperfine coupling has been attributed to a nature of the orbitally dependent exchange interaction between 4f and conduction electrons.