Annealing assisted substrate coherency and high-temperature antiferromagnetic insulating transition in epitaxial La0.67Ca0.33MnO3/NdGaO3(001) films

Abstract

Bulk La0.67Ca0.33MnO3 (LCMO) and NdGaO3 (NGO) have the same Pbnm symmetry but different orthorhombic lattice distortions, yielding an anisotropic strain state in the LCMO epitaxial film grown on the NGO(001) substrate. The films are optimally doped in a ferromagnetic-metal ground state, after being ex-situ annealed in oxygen atmosphere, however, they show strikingly an antiferromagnetic-insulating (AFI) transition near 250 K, leading to a phase separation state with tunable phase instability at the temperatures below. To explain this drastic strain effect, the films with various thicknesses were ex-situ annealed under various annealing parameters. We demonstrate that the ex-situ annealing can surprisingly improve the epitaxial quality, resulting in the films with true substrate coherency and the AFI ground state. And the close linkage between the film morphology and electronic phase evolution implies that the strain-mediated octahedral deformation and rotation could be assisted by ex-situ annealing, and moreover, play a key role in controlling the properties of oxide heterostructures.

Device Performance of the Mott InsulatorLaVO3as a Photovoltaic Material

“…As shown in Fig. 2(b), the sharp and concentrated reflection from the LVO film shares the same in-plane lattice constant as that of the substrate, implying a coherent growth and fully strained state of the LVO film [30][31][32]. The out-of-plane pseudocubic c-axis constant calculated from the RSM data is 4.01Ǻ, which is consistent with the one calculated from the ω-2θ linear scan.…”

Signatures of electronic phase separation in the Hall effect of anisotropically strained La0.67Ca0.33MnO3films

“…The overall behavior and evolution of ρ(T ) of the three samples are consistent with results from previous studies with tuning parameters of thickness and annealing temperature or time [13,14]. It is shown recently that the annealing promotes better coherency with the substrate and enhances the anisotropic strain, thus creating and strengthening the AFI state [40]. Here it is evident that an AFI state is created by the thermal annealing in S2 and S3, as indicated by the sharply rising resistivity with thermal hysteresis below a characteristic temperature, T CO .…”

Evolution and control of the phase competition morphology in a manganite film

“…The magnetotransport measurements were carried out using the four-probe method on a physical property measurement system (Quantum Design) equipped with a motorized horizontal sample rotator, and the magnetic properties were measured on a vibrating sample magnetometer (Quantum Design). Detailed magnetotransport measurements of the films at various thicknesses can be found in refs 19 , 20 , 21 , 30 , 33 .…”

“…Full epitaxial strain state can be induced by the annealing, as shown by the detailed structural characterizations in ref. 21 . ( b ) The ρ - H curves at 150 and 10 K. ( c ) The resistivity during field cooling (FC) at 2.0 T (line) followed by zero-field warming (ZFW) (symbol and line), where a sharp jump is observed at T C ′.…”