Superconductivity and electronic instability at high pressure in Sc5Co4Si10-type compounds

Crystal Growth, Structural Transition, and Magnetic Properties of Ho5Pd4Sn12

Single crystals and polycrystalline samples of Ho₅Pd₄Sn₁₂ have been synthesized using flux and arc-melting methods, respectively. Single-crystal X-ray diffraction studies indicate that Ho₅Pd₄Sn₁₂ crystallizes in a tetragonal structure (I4/m) at room temperature and transforms into a monoclinic structure (C2/m) below ∼194 K. This structural transition is further supported by a transmission electron microscopy study and an anomaly at ∼194 K in the specific heat data. Temperature-dependent resistivity data also show a kink around the structural transition temperature. Ho₅Pd₄Sn₁₂ is antiferromagnetically ordered below 7 K. Ho₅Pd₄Sn₁₂ shows magnetic anisotropy, and the isothermal magnetization curve (H⊥c) at 2 K exhibits a field-induced magnetic phase transition around 22.8 kOe.

Unusual ground states in [Formula: see text] (R = rare earth; T = Rh, Ir; and X = Si, Ge, Sn): a review

Rare earth compounds of the type [Formula: see text] (R  =  rare earth; T  =  Rh, Ir, and X  =  Si, Ge, Sn) display a variety of phase transitions towards exotic states, including charge density waves (CDW), local moment magnetism, antiferromagnetism in the heavy fermion state, superconductivity and giant positive magnetoresistance. They support strongly correlated electron systems. In particular, R ₅Ir₄ [Formula: see text] (R  =  Dy-Lu) exhibit strong coupling CDWs with high transition temperatures, and superconductivity or magnetic ordering at lower temperatures. [Formula: see text] [Formula: see text] (R  =  Gd-Tm; T  =  Co, Rh, Ir) show multiple magnetic transitions with large magnetoresistance below the magnetic transitions. Finally, the light rare earth series [Formula: see text] [Formula: see text] (R  =  Ce, Pr, Nd; T  =  Rh, Ir) display heavy fermion behaviour (for Ce and Pr) or possess giant positive magnetoresistance (for Nd) at low temperatures. This review provides a comprehensive overview of compounds, crystal structures and phase transitions. This is followed by an in-depth discussion of the mechanisms of the phase transitions and the properties of the ordered states.