Magnetic fluctuations in frustrated Laves hydrides R(Mn_{1-x}Al_{x})_{2}H_{y}

By neutron scattering, we have studied the spin correlations and spin fluctuations in frustrated Laves hydrides, where magnetic disorder sets in the topologically frustrated Mn lattice. Below the transition towards short range magnetic order, static spin clusters coexist with fluctuating and alsmost uncorrelated spins. The magnetic response shows a complexe lineshape, connected with the presence of the magnetic inhomogeneities. Its analysis shows the existence of two different processes, relaxation and local excitations, for the spin fluctuations below the transition. The paramagnetic fluctuations are discussed in comparison with classical spin glasses, cluster glasses, and non Fermi liquid itinerant magnets

Pressure-induced long-range magnetic order in the frustrated Laves hydride

We have performed a neutron diffraction study of the magnetic order in the frustrated Laves hydride Tb(Mn0.88Al0.12)2D1.04 under applied pressures up to 8.3 GPa. At 5.9 GPa we observed a first-order magnetic transition accompanied by a volume collapse. The pressure destroys the unusual hydrogen-induced spin-glass magnetic state by suppressing localized magnetic moments in the frustrated Mn sublattice