Spin Nematicity and Large Low‐Field Positive Magnetoresistance in a Half‐Doped Manganite: An Approach Exploiting Cation Size Disorder

Abstract

In principle, material disorder such as random dopants disfavors the long range electronic liquid crystal (ELC) order in quantum matters. It is reported that a minor A site cation size disorder (σ2 = 0.001 Å2) in half‐doped manganites (La1‐xYx)0.5(Ca1‐ySry)0.5MnO3 interestingly leads to spin nematicity which is accompanied by a large positive magnetoresistance (up to 40%) at fields (H ≤ 1 kOe at 60 K) much lower than that (Hcr ≈ 35 kOe) critical for melting the weakened antiferromagnetic charge‐orbital ordering (AFM‐COO). The spin nematicity, emerging with a suppressed orthorhombicity, is ascribed to the destabilization of the d3x2‐r2/d3y2‐r2 orbital stripe alternation and the consequent magnetic symmetry breaking. The non‐trivial low field magneto­resistance is found to be determined by the spin polarized hopping along the nematic filaments and across the perpendicular ferromagnetic zigzag Mn–O chains in the AFM‐COO host. While the present low‐field magneto­resistance holds great potential for future spintronic devices, the approach for spin nematic order based on cation size disorder opens up a new avenue for questing ELC and exotic properties in strongly correlated materials.