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Tailoring magnetic anisotropy in epitaxial half metallic La0.7Sr0.3MnO3 thin films
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10.1063/1.3605542
/content/aip/journal/jap/110/1/10.1063/1.3605542
http://aip.metastore.ingenta.com/content/aip/journal/jap/110/1/10.1063/1.3605542

Figures

Image of FIG. 1.
FIG. 1.

(Color online) Structural characterization of LSMO films grown onto different STO surfaces. XRD scans (inset -scans) around the (220) and (002) crystallographic peaks of 70 nm thick LSMO films grown on nominally flat STO(110) (a) and STO(001) (b) substrates and on a vicinal STO(001) (c) substrate with 10° miscut off the [001] plane toward the . In the scans, note that the double peak is due to the diffraction from the Cu1 and Cu emission lines and that the intensity at the first substrate peak is saturated. (d) -scan around the (002) crystallographic peak of the vicinal LSMO film.

Image of FIG. 2.
FIG. 2.

(Color online) Morphological characterization of LSMO films grown onto different STO surfaces. Left panel: sketches of the crystallographic cell of a LSMO film grown onto nominally flat STO(110) (a) and STO(001) (b) substrates and on a vicinal STO(001) substrate (c). In latter case, the vicinal STO surface is fabricated by cutting the crystal 10° off the [001] plane toward the , thus inducing steps along the [110] crystallographic direction. Corresponding AFM images (central panel, 2 × 2 μ 2) and STM images (right panel, 500 × 500 nm) of a 70 nm thick LSMO film grown onto STO(110) (d)-(g), STO(001) (e)-(h), and vicinal STO(001) (f)-(i). Note that the morphology of the LSMO films is determined by the substrate morphology.

Image of FIG. 3.
FIG. 3.

(Color online) Hysteresis loops of the parallel component of the magnetization ( ()) at  = 0° (filled symbols) and 90° (open symbols), corresponding to the magnetization easy axis (e.a.) and hard axis (h.a.) directions, respectively, of 70 nm thick LSMO films grown onto STO(110) (a), nominally flat STO(001) (b), and vicinal STO (c) substrates. Note that different horizontal field scales have been used. The corresponding STM (300 × 300 nm2) images are shown to illustrate the direct connection between the LSMO film topography and their magnetic properties.

Image of FIG. 4.
FIG. 4.

(Color online) Magnetization reversal study of a 70 nm thick LSMO film grown onto a (110)-oriented STO substrate around the e.a. (left panel) and h.a. (right panel) directions. The corresponding applied field angles are indicated in the graphs. The experimental (H) and loops are given by filled and open circles, respectively. The continuous lines are the corresponding simulated loops determined numerically by the Stoner-Wolfharth model without any free parameters, i.e., by using just the uniaxial anisotropy term derived from the experimental data.

Image of FIG. 5.
FIG. 5.

(Color online) Angular dependence of the normalized remanence magnetization ( / and ) of a 70 nm thick LSMO film grown onto a nominally flat (110)-oriented STO substrate. The inset (bottom graph) shows the polar-plot representation of . The symbols (solid lines) are the experimental (predicted) values derived from the vectorial-resolved Kerr measurements (numerical simulations), as those shown in Fig. 4 .

Image of FIG. 6.
FIG. 6.

(Color online) (a) Angular dependence of the coercive field μ and switching field μ of a 70 nm thick LSMO film grown onto a nominally flat (110)-oriented STO substrate extracted from the vectorial-resolved Kerr measurements, as those shown in Fig. 4 . (b) Comparison of the experimental data (symbols) with the predicted behavior derived from the rotation model (solid lines) and the pinning model (dashed line). The shadowed areas indicate the angular range where reversible rotation processes are the relevant mechanism during reversal.

Image of FIG. 7.
FIG. 7.

(Color online) Magnetization reversal study of the 70 nm thick LSMO film grown onto nominally flat (001)-oriented STO substrate around the e.a. (left panel) and h.a. (right panel) directions. The corresponding applied field angles are indicated in the graphs. The experimental () and loops are given by filled and open symbols, respectively. Notice the change of sign of the loop when the characteristic axes are crossed.

Image of FIG. 8.
FIG. 8.

(Color online) Hysteresis loops of the parallel component of the magnetization ( ()) acquired at the e.a. (a) and h.a. (b) directions of 16 nm, 70 nm, and 120 nm thick LSMO films grown onto vicinal STO(001) substrates. The horizontal axes have been scaled differently. Notice that the anisotropy field increases as the thickness increases.

Image of FIG. 9.
FIG. 9.

(Color online) Magnetization reversal study of the 70 nm thick LSMO film grown onto vicinal 10° STO(001) substrate around the e.a. (left panel) and h.a. (right panel) directions. The corresponding applied field angles are indicated in the graphs. The experimental () and loops are given by filled and open symbols, respectively. The solid lines represent the simulated loops obtained by using a coherent model, which only considers the uniaxial anisotropic term derived from the experimental data.

Image of FIG. 10.
FIG. 10.

(Color online) Thickness-dependent anisotropy field (μ ) derived from the experimental hysteresis loops shown in Fig. 9 (top graph). Bottom graph shows the comparison between the experimental data (symbols) and the numerical simulations described in the text, which consider magnetostatic interaction between interacting magnetic grains (cuboid-like) within different arrays (solid lines). The dimensions of the cuboid are taken from the parameters obtained from the AFM images: length 1 μm, width  = 30 nm, thickness , and intergrain distance 0.2 nm. Insets show the sketch of a single grain and an array of  ×  interacting grains, respectively.

Tables

Generic image for table
Table I.

Measured structural, morphological, and magnetic parameters of LSMO films grown onto (110), (001), and vicinal (001) STO substrates for different thicknesses (). The in-plane and out-of-plane lattice parameters were determined by the XRD measurements (see Sec. III ). (The crystal structure of the films was determined by performing XRD lattice mappings around symmetrical and asymmetrical diffraction peaks. For more details, see Ref. 6 .) Note that, in the case of the (001)-oriented film, the two (equivalent) in-plane axes are the [100] and [010] direction, whereas for the (110)-oriented film the two (inequivalent) in-plane axes are the [001] and direction. The strain is defined by where is the measured lattice parameter of the film, 0.387 nm is the lattice parameter of the unstrained cubic LSMO; and and are the two in-plane components of the strain tensor in case of the LSMO (110)-oriented; is the in-plane component of the strain tensor along the [100] crystallographic direction in case of the (001)-oriented LSMO. The RMS roughness is calculated from the AFM images shown in Fig. 2 . is the saturated magnetization extracted from the magnetization vs. temperature measurements, is the coercive field, and is the anisotropy field determined by the hysteresis loops acquired at room temperature, as indicated in the text (Sec. IV ).

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/content/aip/journal/jap/110/1/10.1063/1.3605542
2011-07-15
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Tailoring magnetic anisotropy in epitaxial half metallic La0.7Sr0.3MnO3 thin films
http://aip.metastore.ingenta.com/content/aip/journal/jap/110/1/10.1063/1.3605542
10.1063/1.3605542
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