Single crystal growth and physical properties of YNi 2B 2C and HoNi 2B 2C

Abstract

The new family of quaternary borocarbide compounds RENi 2B 2C (RE = rare earth) has been studied from the crystal growth point of view. We succeeded in growing large single crystals of YNi 2B 2C and HoNi 2B 2C, 6 mm in diameter and 60 to 110 mm in length, by a floating zone method. These crystals contain no second phase at all. The growth mechanism was investigated by the composition and phase analyses on the feed rod, the molten zone and the grown crystal. D.c. magnetization measurements were performed by a SQUID magnetometer. In the magnetization process of YNi 2B 2C, a pronounced peak effect was observed, which appeared just below the upper critical field H e2 in the reversible region. The appearance of the peak effect depends on the crystallinity and the grain size. Antiferromagnetic order at 5.2 K was observed in the superconducting state of HoNi 2B 2C below 6.5 K, exhibiting the coexistence of antiferromagnetism with superconductivity. In order to study the interplay between superconductivity and magnetism, the magnetization process in magnetic fields parallel to the a- and c-axes was measured. Two meta-magnetic transitions in the magnetic field at 5 and 9 kOe along the a-axis were observed at 2 K.