Control of the charge-ordering-insulating phase in epitaxial La1−xCaxMnO3 (x=0.30–0.45) thin films under the anisotropic strain

Abstract

Articles you may be interested inEffect of growth oxygen pressure on anisotropic-strain-induced phase separation in epitaxial La0.67Ca0.33MnO3/NdGaO3 (001) films

Dynamic phase separation as revealed by the strong resistance relaxation in epitaxially shear-strained La0.67Ca0.33MnO3/NdGaO3(001) thin-films

“…Compared with the pseudocubic structure of LCMO at the given doping level, NGO(0 0 1) substrates supply a suitable edge length [3.865Å for LCMO and 3.867Å for NGO(0 0 1)], but a notable in-plane angle mismatch [89.8641 for LCMO and 89.2651 for NGO(0 0 1)] for the unit cells, producing a large shear strain, or anisotropic strain in orthorhombic notation, for coherent LCMO/ NGO(0 0 1) films [7,15]. To check the structural quality, all the films have been examined by XRD linear scans around the (0 0 2) reflections, as shown in Fig.…”

“…During deposition the temperature and oxygen pressure were fixed at 735 1C and 45 Pa, respectively, and the laser energy density and repetition rate were kept at 2 J/cm 2 and 5 Hz, respectively, resulting in a growth rate of about 6 nm/min. After the growth all the samples were ex-situ annealed at 780 1C in flowing O 2 gas for 5 h, so as to get the various PS states instead of the FMM ground state as verified for all the as-grown films or the bulk counterparts [7]. The magnetotransport properties were measured using the four-probe method on a Quantum Design physical property measurement system.…”

“…Also, for epitaxial Pr 0.5 Sr 0.5 MnO 3 films the COI phase transition gets lost when they were grown on cubic (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 (0 0 1), but it can be recovered if the (1 1 0)-cut substrates are employed [5,6]. By contrast, for La 0.67 Ca 0.33 MnO 3 (LCMO), doped safely for a ferromagnetic metal (FMM) ground state, we have recently demonstrated that the COI phase with a high transition temperature can be induced by anisotropic (shear) strain when the films were grown coherently on orthorhombic (0 0 1)-cut NdGaO 3 [NGO(0 0 1)] substrates [7]. Therefore, it is very effective to control the physical properties of manganite thin films through strain engineering from the variety of substrates.…”

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

“…29,32 The ceramic LCMO target was prepared by standard solid state reactions. During deposition, the substrate temperature and O 2 pressure were 735…”

“…More strikingly, though the bulk LCMO is optimally doped in the ferromagnetic-metal (FM) ground state, the LCMO/NGO(001) films, after being annealed in oxygen atmosphere, show an antiferromagnetic insulator phase transition at ∼250 K and the PS with the coexistence of antiferromagnetic-insulating (AFI) and FM phases at the temperature below. [32][33][34][35] In the early work we have demonstrated that the ex-situ annealing process and the NGO(001) substrate stabilized in-plane anisotropic strain state are both indispensable for the formation of AFI phase. 34,35 However, the detailed evolutions of the strain state and octahedral behavior during annealing, which are central for understanding the AFI phase and PS, are still unclear.…”