We observed the conduction electron spin resonance (CESR) in fine powders of both in the superconducting and normal states. The Pauli susceptibility is in the temperature range of 450 to . The spin relaxation rate has an anomalous temperature dependence. The CESR measured below at several frequencies suggests that is a strongly anisotropic superconductor with the upper critical field, , ranging between 2 and . The high-field reversible magnetization data of a randomly oriented powder sample are well described assuming that is an anisotropic superconductor with .
- Received 27 April 2001
- Published 10 July 2001
© 2001 The American Physical Society