Peak Effect in Single Crystalline YNi2B2C

Abstract

Dc-magnetization and ac-susceptibility measurements have been performed on new quarternary intermetallic compound YNi2B2C single crystals grown by the floating zone method. In the magnetization process, a pronounced peak effect was observed, which appears just below the upper critical field H c2 in the reversible region. It turns out that the appearance of the peak effect depends on the crystallinity and the size of the grains in the sample. This effect suggests that the peak effect in YNi2B2C may not be intrinsic origin of the nature of superconductivity, but may be rather related to the extrinsic origin such as the Pippard-mechanism[1], which has been thought to be responsible for the peak effect often observed in many conventional type II superconductors just below H c2. Nevertheless, the sharp appearance(disappearance) is reminiscent of the first order phase transition similar to the recently observed anomalous peak effect in CeRu2, UPt3 and UPd2Al3. The magnetic phase diagram of YNi2B2C is established and is argued in comparison with the recent theoretical work by Tachiki et al. [2].