Susceptibility, magnetisation and critical behaviour of a magnetic superconductor:Y₉Co₇

The authors present detailed measurements of the AC susceptibility and magnetisation as functions of temperature and magnetic field for the magnetic superconductor Y 9 Co 7 and compare them with the mean-field theories and the self-consistent renormalisation theory of spin fluctuations. They have also determined the critical exponents beta and gamma from the asymptotic relations for the critical behaviour of the magnetisation and susceptibility. They have been further evidence that the weak itinerant ferromagnetism of the intermetallic compound Y 9 Co 7 is of double character with two groups of Co magnetic behaviour. Comparing the magnetisation data with the theory they have extended the zero-field magnetisation curve up to 0K, finding further evidence of the coexistence of ferromagnetism and superconductivity.