Microscopic measurements on the band 5f-metamagnetism in UCoAl

We have carried out 27Al nuclear magnetic resonance (NMR) and 59Co NMR and nuclear quadrupole resonance (NQR) measurements on UCoAl, which exhibits a meta-magnetic transition in a small magnetic field (H∼1 T) at around 16 K. Besides 27Al and 59Co NMR signals, two kinds of 59Co-NQR signals corresponding to the two inequivalent Co sites in UCoAl were observed. The temperature dependence of the nuclear spin-lattice relaxation rate (T1−1) in 59Co-NQR shows a similar behavior to the exchange enhanced paramagnet Co(S1−xSex)2 with the temperature-induced local moment discussed by the spin fluctuation theory. The field- and temperature-dependence of T1−1 and the nuclear spin–spin relaxation rate (T2−1) show strong magnetic anisotropy in this compound.