Pseudomorphic strain induced strong anisotropic magnetoresistance over a wide temperature range in epitaxial La0.67Ca0.33MnO3/NdGaO3(001) films

Abstract

Strong anisotropic magnetoresistance (AMR) was observed in La0.67Ca0.33MnO3 films grown coherently on the orthorhombic NdGaO3(001) substrates. With an increased orthorhombic lattice distortion due to the pseudomorphic strain, the films show not only a ferromagnetic-metal (FM) transition at TC of ∼265 K, but also the phase coexistence of FM and antiferromagnetic-insulator below ∼250 K. The phase competitions are very sensitive to the magnetic field, and more strikingly, to its orientations with respect to the crystal axes resulting in a large AMR in a broad temperature range, in addition to the conventional one peaked near TC. The films also show uniaxial magnetic anisotropy with the easy axis along the elongated b axis, suggesting that it is the strain induced spin-orbit-lattice coupling and the resultant phase competitions that control the AMR in epitaxial manganite films.

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

“…In fact, by comparing the magnetotransport properties of LCMO films grown on the NGO substrates with various orientations, we have excluded the interfacial chemical diffusion and variation of La:Ca doping ratio during ex-situ annealing, and demonstrated that the AFI phase is elastic-driven. 33,35 In Fig. 1(c), the ω-2θ linear scans of the 10-h annealed films (20 and 40 nm) show sharp Laue fringes, further confirming that the LCMO films have high crystal quality and sharp interface with the underlying substrates.…”

“…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.…”

Phase separation and enhanced magnetoresistance in the strained epitaxial La0.625Ca0.375MnO3 (001) films

“…By contrast, the film deposited at 30 Pa has a large value over a broad temperature below the T C , where the CMR and AMR dependence on temperature display a complex thermal hysteresis, attributing to the strong competition between FM and AFI phase in the cooling or heating process. 10 At the same time, the monotonous behavior for CMR together with the nonmonotonic behavior for AMR was observed in both films in an increasing magnetic field. In Fig.…”

“…1,[4][5][6] The behavior of a charge-ordered antiferromagnetic-insulator (AFI) in manganite films can be controlled with the epitaxial strain evolution, 1,2,7,8 even in which were doped for a ferromagnetic-metal (FM) ground state. [9][10][11] Anisotropic magnetoresistance (AMR) in manganites also could be enhanced dramatically under a tensile or compressive strain at around the Curie temperature (T C ), 12 but the AMR dependence on magnetization displays nonmonotonic behavior different from the colossal magnetoresistance (CMR). [12][13][14] Due to its high sensitivity to the relative orientation between the applied magnetic field and the crystal axes, the AMR of manganites have the potential to make the functional magnetic devices.…”

Unusual anisotropic magnetoresistance in charge-orbital ordered Nd0.5Sr0.5MnO3 polycrystals

“…14,16,17 In recent years, special attention has been paid to perovskite manganites where very large AMR has been observed. 5,[18][19][20][21][22][23] The AMR shows different temperature and magnetic field dependence as compared to that in 3d ferromagnetic alloys, suggesting different mechanisms behind. In contrast to that in 3d ferromagnetic alloys, the crystalline component of AMR in perovskite manganites can be very large, and a large resistance change can be observed even by rotating H in the plane that is perpendicular to I [out-of-plane AMR, Fig.…”