Field-induced magnetic phase transitions and correlated electronic states in the hexagonal RAgGe and RPtIn series
Rare earth intermetallic compounds provide rich grounds for investigating the properties of both local moment and strongly correlated, hybridized moment systems. These areas have been intensively explored mostly on cubic and tetragonal intermetallic compounds, and very little work existed on materials with lower symmetry. Moreover, a large number of Ce-based heavy fermion compounds have been studied, whereas the analogous Yb-based ones are much rarer. We thus wanted to study local moment metamagnetism and Yb-based heavy fermion physics in hexagonal systems.;The RAgGe and RPtIn series belonging to the Fe2P family of hexagonal compounds allowed us to perform such studies on both local moment and strongly correlated, hybridized moment systems. The RAgGe and RPtIn compounds presented in this work display anisotropy temperature and field dependent magnetization due to the crystalline electric field (CEF) splitting of the Hund's rule ground state multiplet. The TmAgGe and TbPtIn members of these series display extreme planar anisotropy, which makes them well suited for a study of the angular dependent metamagnetism. We developed the three co-planar Ising-like systems model, which allowed us to determine the net distribution of the magnetic moments in the two compounds.;The YbAgGe and YbPtIn compounds have some properties distinct from the rest of their respective series: having low ordering temperatures and enhanced electronic specific heat coefficient gamma, they can be classified as stoichiometric, Yb-based heavy fermion compounds, with a magnetic field-induced quantum critical point QCP. In the former compound, a non-Fermi liquid-like NFL regime is apparent at intermediate fields, but such a behavior is more ambiguous in the YbPtIn. However, a small Pt-deficiency in flux-grown YbPt0.98In single crystals seems to stabilize, together with the magnetic field, a non-Fermi liquid-like NFL regime.;In summary, TmAgGe and TbPtIn are hexagonal compounds revealing complex, and yet intelligible angular dependent metamagnetism; together with the quantum critical physics found in YbAgGe and YbPtIn, the RAgGe and RPtIn series dramatically confirm the fertile grounds for research that can be found in these hexagonal systems.