Synthesis and physical properties of perovskite SmSrNiO(= 0, 0.2) and infinite-layer SmSrNiOnickelates.

Recently, superconductivity at about 9-15 K was discovered in NdSrNiO(Nd-112,≈ 0.125-0.25) infinite-layer thin films, which has stimulated enormous interests in related rare-earth nickelates. Usually, the first step to synthesize this 112 phase is to fabricate theNiO(-113,: rare-earth element) phase, however, it was reported that the 113 phase is very difficult to be synthesized successfully due to the formation of unusual Nioxidation state. And the difficulty of preparation is enhanced as the ionic radius of rare-earth element decreases. In this work, we report the synthesis and investigation on multiple physical properties of polycrystalline perovskites SmSrNiO(= 0, 0.2) in which the ionic radius of Smis smaller than that of Prand Ndin related superconducting thin films. The structural and compositional analyses conducted by x-ray diffraction and energy dispersive x-ray spectrum reveal that the samples mainly contain the perovskite phase of SmSrNiOwith small amount of NiO impurities. Magnetization and resistivity measurements indicate that the parent phase SmNiOundergoes a paramagnetic-antiferromagnetic transition at about 224 K on a global insulating background. In contrast, the Sr-doped sample SmSrNiOshows a metallic behavior from 300 K down to about 12 K, while below 12 K the resistivity exhibits a slight logarithmic increase. Meanwhile, from the magnetization curves, we can see that a possible spin-glass state occurs below 12 K in SmSrNiO. Using a soft chemical reduction method, we also obtain the infinite-layer phase SmSrNiOwith square NiOplanes. The compound shows an insulating behavior which can be described by the three-dimensional variable-range-hopping model. And superconductivity is still absent in the polycrystalline SmSrNiO.