Antiferro- And metamagnetism in the S=7/2 hollandite analog EuGa2Sb2

Recent work analyzing the impact of nonsymmorphic symmetries on electronic states has given rise to the discovery of multiple types of topological matter. Here we report the single-crystal synthesis and magnetic properties of EuGa2Sb2, a Eu-based antiferromagnet structurally consisting of pseudo-1D chains of Eu ions related by a nonsymmorphic glide plane. We find the onset of antiferromagnetic order at TN=8K. Above TN the magnetic susceptibility is isotropic. Curie-Weiss analysis suggests competing ferromagnetic and antiferromagnetic interactions, with peff=8.1μB as expected for 4f7 J=S=7/2 Eu2+ ions. Below TN and at low applied magnetic fields, an anisotropy develops linearly, reaching χ/χ=6 at T=2K. There is concomitant metamagnetic behavior along χ, with a magnetic field of μ0H≈0.5 T sufficient to suppress the anisotropy. Independent of crystal orientation, there is a continuous evolution to a field-polarized paramagnetic state with M=7μB/Eu2+ at μ0H=2 T as T→0K. Specific-heat measurements show a recovered magnetic entropy of ΔSmag≈16.4Jmol-1K-1 from T∼0 K to T=TN, close to the expected value of Rln(8) for an S=7/2 ion, indicating negligible low-dimensional spin fluctuations above TN. We find no evidence of unusual behaviors arising either from the dimensionality or the presence of the nonsymmorphic symmetries.