Dynamics of Frustrated Magnetic Moments in Antiferromagnetically Ordered TbNiAl Probed by Spin Echo and Time-of-Flight Spectroscopy

In this contribution we present a combined study of the dynamics of frustrated Tb spins in the intermetallic compound TbNiAl by means of neutron time-of-flight and spin echo spectroscopy. It is a remarkable and very unusual characteristic of TbNiAl that its afm phase (below T N = 47 K) contains regular long-range ordered spins as well as frustrated spins. The latter are identified by a strongly reduced moment measured by neutron diffraction. Our quasielastic measurements show that the frustrated moments relax on a time scale of 0.01 ns to 0.1 ns. Their auto-correlation function I(Q, t) is Q-independent and exponential in time.