The synthesis and crystallographic and physical properties of polycrystalline EuNiGe${}_3$ are reported. EuNiGe${}_3$ crystallizes in the noncentrosymmetric body-centered tetragonal BaNiSn${}_3$-type structure (space group $I4mm$), in agreement with previous reports, with the Eu atoms at the corners and body center of the unit cell. The physical property data consistently demonstrate that this is a metallic system in which Eu spins $S=7/2$ order antiferromagnetically at a temperature $T_{\mathrm{N}}=13.6$ K. Magnetic susceptibility $\chi$ data for $T>T_{\mathrm{N}}$ indicate that the Eu atoms have spin 7/2 with $g=2$, that the Ni atoms are nonmagnetic, and that the dominant interactions between the Eu spins are ferromagnetic. Thus we propose that EuNiGe${}_3$ has a collinear A-type antiferromagnetic structure, with the Eu ordered moments in the $ab$ plane aligned ferromagnetically and with the moments in adjacent planes along the $c$ axis aligned antiferromagnetically. A fit of $\chi (T\le T_{\mathrm{N}})$ by our molecular field theory is consistent with a collinear magnetic structure. Electrical resistivity $\rho$ data from $T_{\mathrm{N}}$ to 350 K are fitted by the Bloch-Grüneisen model for electron-phonon scattering, yielding a Debye temperature of 265(2) K. A strong decrease in $\rho$ occurs below $T_{\mathrm{N}}$ due to loss of spin-disorder scattering. Heat capacity data at $25\mathrm{K}\le T\le 300$ K are fitted by the Debye model, yielding the same Debye temperature 268(2) K as found from $\rho \left(T\right)$. The extracted magnetic heat capacity is consistent with $S=7/2$ and shows that significant short-range dynamical spin correlations occur above $T_{\mathrm{N}}$. The magnetic entropy at $T_{\mathrm{N}}=13.6$ K is $83\%$ of the expected asymptotic high-$T$ value, with the remainder recovered by 30 K.

• Received 15 November 2012

DOI:https://doi.org/10.1103/PhysRevB.87.064406