Fe b 19 98 Pressure Effect on the Spin Fluctuations in YMn 2 – Mn NQR Study –

We report the NQR study on the pressure-induced paramagnetic state in the antiferromagnetic (AF) intermetallic compound YMn2 with the Néel temperature TN=100 K at ambient pressure. From the T variation of the nuclear spin-lattice relaxation rate, (1/T1) of Mn above the critical pressure of 4 kbar, the spin fluctuation feature is found to change below a temperature Tsf. At higher temperature than Tsf, the nuclear relaxation behavior is well described in terms of the self-consistent renomalized (SCR) spin fluctuation theory for nearly AF metals, whereas below Tsf a deviation is significant and 1/T1T exhibits a weak T variation. It is pointed out that Tsf coincides with the temperature below which a T 2 law in electrical resistivity is valid as expected for a Fermi liquid ground state. We proposed that these features are understood from the standpoint that the development of AF spin fluctuation remains in short-range associated with the singlet formation among Mn spins in each tetrahedron as suggested by the inelastic neutron experiments on Y1−xScxMn2. Typeset using REVTEX