Wydarzenia

Seminarium Oddziału Badań Magnetyków

Heavy fermion behavior and magnetic ordering in Ce(Cr,Ti)Ge₃ with hexagonal perovskite structure

dr Debarchan Das

Department of Physics, Indian Institute of Technology Kanpur, India and Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany

Strongly correlated electron systems have attracted considerable attention as they exhibit many exotic properties which include heavy fermion behavior, quantum phase transition and high temperature superconductivity. Among the vast number of existing intermetallic compounds, some Ce-, Yb- and U-based compounds show large enhancement of the conduction electron effective mass at low temperature, known as heavy fermion systems. Some of the heavy fermion compounds exhibit superconductivity of unconventional nature in which magnetism has an important role to play. Usually, unconventional superconductivity occurs in heavy fermion compounds close to the magnetic–nonmagnetic boundary. In our effort to search for novel Ce-compounds having potential to exhibit interesting physical properties we have synthesized polycrystalline samples of CeCrGe₃ and performed a comprehensive study of the low temperature properties by means of x-ray absorption spectroscopy (XAS), magnetic susceptibility, isothermal magnetization, electrical resistivity, specific heat and thermoelectric power measurements. The results corroborate that the compound undergoes a ferromagnetic transition below T_C ~ 70 K. The Kondo lattice type of the resistivity and the large value of Sommerfeld coefficient (γ = 130mJ/mol/K²) strongly suggest that CeCrGe₃ is a moderate heavy fermion system. The observation of HF/Kondo lattice behavior in the ferromagnetically ordered state is quite rare. In order to gain further information on the magnetic ordering of CeCrGe₃, we have performed muon spin relaxation (μSR) experiments which reveal the presence of a long range magnetically ordered state. Moreover, we have carried out powder neutron diffraction study on CeCrGe₃ to determine the magnetic structure which turns out to be quite interesting. In addition, we have tried to tune the magnetic ordering by Ti doping in place of Cr in CeCrGe₃. The results on CeCr_1-xTi_xGe₃ suggest a possible existence of a bi-critical point in the system. Superconductivity was not observed down to 2 K.