Tailoring magnetic anisotropy in epitaxial half metallic La0.7Sr0.3MnO3 thin films

Abstract

We present a detailed study on the magnetic properties, including anisotropy, reversal fields, and magnetization reversal processes, of well characterized half-metallic epitaxial La 0.7 Sr 0.3 MnO 3 (LSMO) thin films grown onto SrTiO 3 (STO) substrates with three different surface orientations, i.e., (001), (110), and (118). The latter shows step edges oriented parallel to the [110] (in-plane) crystallographic direction. Room temperature high resolution vectorial Kerr magnetometry measurements have been performed at different applied magnetic field directions in the whole angular range. In general, the magnetic properties of the LSMO films can be interpreted with just the uniaxial term, with the anisotropy axis given by the film morphology, whereas the strength of this anisotropy depends on both structure and film thickness. In particular, LSMO films grown on nominally flat (110)-oriented STO substrates presents a well defined uniaxial anisotropy originated from the existence of elongated in-plane [001]-oriented structures, whereas LSMO films grown on nominally flat (001)-oriented STO substrates show a weak uniaxial magnetic anisotropy, with the easy axis direction aligned parallel to residual substrate step edges. Elongated structures are also found for LSMO films grown on vicinal STO(001) substrates. These films present a well-defined uniaxial magnetic anisotropy, with the easy axis lying along the step edges, and its strength increases with the LSMO thickness. It is remarkable that this step-induced uniaxial anisotropy has been found for LSMO films up to 120 nm thickness. Our results are promising for engineering novel half-metallic magnetic devices that exploit tailored magnetic anisotropy.

Magnetization reversal in half metallic La0.7Sr0.3MnO3 films grown onto vicinal surfaces

“…12,13 Moreover, by using vicinal surfaces we can fabricate artificially periodic stepped surfaces with in-plane magnetic anisotropy. 14 In vicinal substrates, the surfaces are intentionally misoriented to a (near) low index surface, therefore determining surface step edges. In such a way, the high symmetry of the low index surface is broken and an additional uniaxial anisotropy is expected.…”

“…The vicinal angle h v was from the [001] surface toward the ½1 10 crystallographic direction, thus inducing step edges along the ½110 direction. 14 The laser fluence was 1-2 J cm À2 , the target-to-substrate distance, the oxygen pressure, and the substrate temperature were optimized to 50 mm, 0.35 mbar, and 720 C, respectively. 9 The crystal structure was investigated by means of x-ray diffraction (XRD).…”

“…It is worth noting that in all the investigated samples, the Curie temperature was always found above RT. 14 The morphology of the samples was investigated at RT by means of atomic force (AFM) and scanning tunnel microscopies, using a Nanoscope microscope. The average roughness (rms) of the samples was found always in the range of few unit cells.…”

Magnetic Sensors Based on AMR Effect in LSMO Thin Films

“…Different magnetic anisotropies could be induced in the LSMO films depending on the substrate type, as previously shown in [4]. The magnetoresistance versus magnetic field in the case of a stripe patterned in a 50 nm thick LSMO film deposited on STO (001) and aligned at 45° with respect to the easy axis direction is shown in Figure 2.…”

Probing La0.7Sr0.3MnO3multilayers via spin wave resonances

“…Previous studies have noted both uniaxial and biaxial anisotropies present in STO/LSMO films, with the biaxial anisotropy originating from the cubic symmetries of epitaxial LSMO grown on (001) STO and the uniaxial anisotropies originating from physical steps on the STO surface [13,[34][35][36]. It was reported that the in-plane fourfold and two-fold anisotropies are bulk in origin and not strongly related to interface pinning.…”