Investigation of the antiferromagnetic order in superconducting nickelates

Recently, superconductivity has been surprisingly reported at 15 K in Sr-doped NdNiO2 suggesting the existence of a new family of high-temperature superconductors. The structure of this nickel oxide consists in a stacking of NiO2 layers separated by rare-earth spacer layer, stabilizing the unusual Ni1+ oxidation state, corresponding to 3d9 electronic configuration, similarly to the cuprates. Our previous experiment on WISH @ ISIS, brought evidence for a AF order with a propagation vector of q_AF=(1/2,1/2,0), in two samples, a pure and 5% Sr-doped (Nd,Sr)NiO2 that could be at the origin of magnetic fluctuations playing a key role in the emergence of superconductivity. We first proposed to establish if this magnetic order is related to Nd or Ni atoms by studying LaNiO2 analogue. Then we proposed to precisely study the temperature dependence of the magnetic order and its possible connection to the low temperature upturn reported in resistivity in the (Nd1-xSrx)NiO2 with x=0,0.05.
WISH beamline is perfectly suited for magnetic structure determination and temperature evolution study. The study will be done at five chosen temperatures in the range 1-100K for the three samples, (Nd1-xSrx)NiO2 with x=0,0.05 and LaNiO2. Based on the previous experiment characteristics, we expect to count 4h per temperature. We thus ask for 3 days on the WISH high-resolution cold-neutron powder diffractometer to carry out our investigations

近期，研究人员在锶掺杂NdNiO₂（Sr-doped NdNiO2）中于15开尔文下意外观测到超导现象，这预示着一类全新的高温超导体（high-temperature superconductor）家族的存在。该镍氧化物（nickel oxide）的结构由NiO₂层堆叠而成，层间以稀土间隔层（rare-earth spacer layer）分隔，可稳定非常规的Ni⁺¹氧化态，对应3d⁹电子构型，这一点与铜酸盐（cuprates）类似。
我们此前在WISH@ISIS上开展的实验为两个样品（纯相及5%锶掺杂的(Nd,Sr)NiO₂）中存在传播矢量为q_AF=(1/2,1/2,0)的反铁磁序（AF order）提供了实验证据，该磁序可能是触发超导现象的关键磁涨落的起源。我们首先计划通过研究LaNiO₂类似物（LaNiO2 analogue），明确该磁序源于钕原子还是镍原子；随后拟精准表征磁序的温度依赖性，以及其与x=0、0.05的(Nd₁₋ₓSrₓ)NiO₂体系中电阻率低温上升现象的潜在关联。
WISH束流线（WISH beamline）非常适用于磁结构测定与温度演化研究。本研究将针对三个样品（x=0、0.05的(Nd₁₋ₓSrₓ)NiO₂及LaNiO₂），在1~100开尔文范围内选取五个温度点开展实验。基于此前实验的参数特征，我们预计每个温度点的计数时长为4小时。因此，我们申请使用WISH高分辨冷中子粉末衍射仪（cold-neutron powder diffractometer）开展本研究，实验机时共计3天。