Epitaxial growth and properties of La0.7Sr0.3MnO3 thin films with micrometer wide atomic terraces

Abstract

Abstract:La 0.7 Sr 0.3 MnO 3 (LSMO) films with extraordinarily wide atomic terraces are epitaxially grown on SrTiO 3 (100) substrates by pulsed laser deposition. Atomic force microscopy measurements on the LSMO films show that the atomic step is ~ 4 Å and the atomic terrace width is more than 2 µm. For a 20 monolayers (MLs) LSMO film, the magnetization is determined to be 255 ± 15 emu/cm 3 at room temperature, corresponding to 1.70 ± 0.11 µ B perMn atom. As the thickness of LSMO increases from 8 MLs to 20 MLs, the critical thickness for the temperature dependent insulator-to-metal behavior transition is shown to be 9 MLs.Furthermore, post-annealing in oxygen environment improves the electron transport and magnetic properties of the LSMO films. has been widely used for efficient spin injection in organic spin valves [3][4][5][6][7][8] and giant tunneling magnetoresitance in magnetic tunnel junctions [9,10]. Regarding the synthesis of thin LSMO films, pulsed laser deposition (PLD) has been found to be a promising method to achieve high quality films with atomic scale variations [11][12][13][14]. Common to strongly correlated oxide materials, the intriguing magnetic and electron transport properties of LSMO are intimately related to the spin-lattice-charge couplings, which are sensitive to strain, growth condition, and the thickness of the films [14,15]. For example, the magnetic anisotropy of LSMO has been shown to be in-plane when it is grown on SrTiO 3 (STO) substrates but out-of plane on LaAlO 3(LAO) substrates [16,17]. Strain effect has also been found to play a critical role in the electron transport properties via growing LSMO on various perovskites, including STO, LAO, DyScO 3 , and NdGaO 3 [18,19]. Furthermore, the magnetic and electron transport properties of the LSMO films are also shown to be highly dependent on the growth condition such as the oxygen pressure [11,12]. As single terraces of ferromagnetic films with desired spin structures have the potential to create future spintronics devices, the atomic level control of the magnetic oxide thin films with wide atomic terraces is emergent. However, in previous reports, the terraces of these LSMO films are only several hundred nanometers wide [12,15] and the study of epitaxial LSMO films with micrometer wide atomic terraces has been lacking.In this letter, we report the growth of LSMO films with extraordinarily wide atomic terraces of more than 2 µm on STO (100) intensity shows a minimum value, which indicates the growth of an half ML LSMO film. Then the RHEED intensity starts to increase and reaches a maximum value at ~249 seconds and this indicates the growth of a full ML film. At ~1820 seconds, the shutter is closed and the measurement of the RHEED intensity is stopped. The total 10 peaks of the RHEED intensity oscillation curve indicate the growth of exact 10 MLs LSMO film on the top of the STO substrate. After the growth, the RHEED pattern of the 10 MLs LSMO film at 700 °C is shown in figure 1d. The RHEED pattern is very sharp and streaky, indicati...

Tunable perpendicular exchange bias in oxide heterostructures

“…Interestingly the saturation magnetization per ferromagnetic layer, 2×SrMnO 3 + 4×LaMnO 3 , varies with different types of cuprate spacers; the structure with LCO layers shows the largest magnetic moments, and chemical substitution in the LCO layers reduces the magnetization. The depth-resolved profile of the in-plane magnetic moment obtained from PNR agrees with the low magnetization in the δ-3ML sample, where the magnetic moment reaches up to 0.8 µ B , that is, less than half of the value ∼2 µ B in optimally doped LSMO thin films (Figure 3) 21,22 . The origin of the reduced magnetism can be attributed to an interface effect, because the nominal compositions of the ferromagnetic layers are identical.…”

Epitaxial growth and magnetic/transport properties of La0.7Sr0.3MnO3 thin films grown on SrTiO3 with optimized growth conditions

“…A minimum value of resistance was achieved for the substrate growth temperature of 750 C. Meanwhile it was found that over one hundred MLs thick LSMO lms have higher metal-insulator transition point and smaller resistivity as compared to those of under 20 MLs thick LSMO lms as reported previously. 28 The overlapping curves corresponding to substrate growth temperatures of 800 and 850 C are similar to the case of M-T patterns as shown in Fig. 5(a).…”

Evidence of weak localization in quantum interference effects observed in epitaxial La0.7Sr0.3MnO3 ultrathin films

“…At the end of deposition, the film was cooled down at the growth pressure without further annealing. With the help of ozone26, the epitaxial thin films have good quality with no need for post-annealing27.…”