Speaker
Description
The uranium based intermetallics are intensively studied because of dual character of uranium
5f electrons. Unique coexistence of ferromagnetism and superconductivity has been revealed
in URhGe and UCoGe crystalizing in the orthorhombic TiNiSi-type structure. Since UCoGe
(T C =2.5 K) is very close to magnetic instability, it is a candidate to observe vanishing of
ferromagnetic order and ferromagnetic quantum critical point. The chemical substitution was
found as an effective tool to destabilize the ferromagnetic order in UCoGe by substitution on
Co site by transition metal. UCo 1-x Ru x Ge or UCo 1-x Fe x Ge systems have showed vanishing of
ferromagnetism in quantum critical point at critical concentration 30 % of substituent
element. However, in UCo 1-x Rh x Ge or UCo 1-x Pd x Ge where both parent compounds order
magnetically, finite ordering temperature is conserved, thus quantum critical phenomena have
not been observed.
We have decided to investigate UCo 1-x Ir x Ge system. Since UCoGe is ferromagnet and UIrGe
antiferromagnet, its alloy system is promising candidate to observe interesting evolution of
magnetism. We will show that UCo 1-x Ir x Ge is the first case of disappearance ordering
temperature between two magnetic parent compounds. Therefore, two quantum critical point
of different nature of ferromagnetic and antiferromagnetic-type are expected.
In order to investigate evolution of the magnetism we have prepared polycrystalline samples
throughout whole concentration range. Subsequently, we have performed measurements of
magnetization, electrical resistivity and heat capacity.
