Magnetic ordering in frustrated Ce₅Ni₂Si₃

The transport, magnetic, and thermal properties are studied on an antiferromagnetic compound Ce₅Ni₂Si₃ with T_N=7.3 K. We find signatures of spin fluctuation in this geometrically frustrated magnet. The Curie-Weiss fit gives a large value of the paramagnetic Curie temperature, yielding a frustration parameter f≃8.4. The electronic specific heat coefficient γ=300 mJ/Ce mol K² is strongly enhanced, leading to residual entropy at low temperatures. The spin fluctuation is suppressed as the magnetic field exceeds the metamagnetic transition field H_m=1 T, where the magnetoresistance decreases steeply. The steady increase of magnetic susceptibility below T_N is likely to be associated with the presence of paramagnetic Ce ions. For La ₅Ni₂Si₃, a superconducting transition is observed at T_c=1.8 K.