UCoA1 has a paramagnetic ground state, although the c-axis susceptibility shows a maximum at Tmax ≈ 20 K. The low-T state is easily modified to ferromagnetism by application of magnetic field along the c-axis or by doping by suitable elements. The field and temperature dependences of the magnetization and specific heat of single crystals of the UCo1-xTxAl (T = Fe, Ni) solid solutions are presented. All the compounds exhibit a strong uniaxial anisotropy with the dominant magnetic response along the oaxis of the hexagonal ZrNiAl-type structure. Ni substitution yields an increase of the critical field for metamagnetism which disappears at x = 0.10. UCo0.95Fe0.05Al is ferromagnetic below 30 K. UCo0.98Fe0.02Al and UCo0.95Fe0.05Ni0.05Al exhibit ferromagnetism with a significant trace of metamagnetism. An analysis of specific-heat data for UCoAl and UCo0.95Ni0.05Al in 0 and 10 T allows the entropy contributions due to spin fluctuations to be extracted.
- Spin fluctuations