Observation of Large Low-Field Magnetoresistance in Layered (NdNiO₃)_n:NdO Films at High Temperatures

Large low-field magnetoresistance (LFMR, < 1 T), related to the spin-disorder scattering or spin-polarized tunneling at boundaries of polycrystalline manganates, holds considerable promise for the development of low-power and ultrafast magnetic devices. However, achieving significant LFMR typically necessitates extremely low temperatures due to diminishing spin polarization as temperature rises. To address this challenge, one strategy involves incorporating Ruddlesden-Popper structures (ABO₃)_n:AO, which are layered derivatives of perovskite structure capable of potentially inducing heightened magnetic fluctuations at higher temperatures. Here, a remarkable LFMR of up to 1.0×10³% is obtained in the layered (NdNiO₃)_n:NdO films with a high and wide temperature range (190-240 K). This finding underlines that the layered (NdNiO₃)_n:NdO (n = 1) structure show a complex magnetic structure above T_MI of perovskite NdNiO₃, where small ferromagnetic domains are embedded in the antiferromagnetic domains, raising the tunneling barriers and magnetic fluctuations at high temperatures. Furthermore, applying a low magnetic field (<0.1 T) near T_MI effectively mitigates the disruption of antiferromagnetic order structures at boundaries, then a higher temperature is required to break the inhibition of ferromagnetic to antiferromagnetic phase transition. The results contribute significantly to the advancement of magnetic devices capable of achieving substantial LFMR at room temperature.