The class of quaternary intermetallic superconductors of the RNi2B2C (R — rare earth) type, first discovered in 1994 [1, 2], is of primary interest due to its exhibition of the interplay between superconductivity and magnetic ordering phenomena. The series admits several arrangements of magnetic ordering temperature and superconducting transition temperature, including
no magnetic ordering at all, which is the case for YNi2B2C. This compound is ideal, therefore, to study the fundamental superconducting properties of the series, uninfluenced by magnetic effects. HoNi2B2C undergoes magnetic ordering at 6.1K, below its superconducting transition at 9K, due to the 10μB magnetic moment of the Ho3+ ion, and an anisotropic magnetic phase diagram of the material has been proposed  based on experiments on bulk materials. Several groups are involved in the preparation of thin films of these materials by various techniques [4, 5, 6]. The availability of c-axis oriented or epitaxial thin films enables important experiments to be performed probing the anisotropic properties of the material. Here, we report on the angular dependence of the upper critical field of HoNi2B2C at various temperatures, and compare the results with those obtained on non-magnetic YNi2B2C.
Rare earth transition metal borocarbides (nitrides): superconducting, magnetic and normal state properties, Edited by K.-H. Müller, V. Narozhnyi, 01/2001: pages 363-368; Kluwer Academic Publishers, Dordrecht., ISBN: 0-7923-6879-7