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Dive into the research topics where G.T. Pérez is active.

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Featured researches published by G.T. Pérez.


Journal of Magnetism and Magnetic Materials | 1996

Effects of the initial stages of film growth on the magnetic anisotropy of obliquely-deposited cobalt thin films

J.M. Alameda; F. Carmona; F.H. Salas; L.M. Álvarez-Prado; R. Morales; G.T. Pérez

Abstract We have studied the in-plane magnetic anisotropy in polycrystalline cobalt films, which were obliquely deposited by e-beam evaporation in UHV at T s = 300 K. Three film series were studied, with average film thicknesses t = 15, 45 and 100 nm. For all cases, the incidence angle of the vapor beam with respect to the surface normal was α = 0, 30, 40, 50, 60 and 70°. At normal incidence, the anisotropy and the coercive fields were found to be H K = 15–25 Oe, and H c ⋍ 25 Oe , independent of the film thickness. In all series it has been observed that, as α increases, the easy axis of in-plane anisotropy switches from perpendicular to parallel with respect to the incidence plane of atoms during film deposition. For t = 15 nm, such a transition occurs at α t ⋍ 70° , whereas for larger values of t we found that α t = 60°. At constant film thicknesses, H K and H c increase with increasing α; the lower the film thickness, the sharper this effect, e.g. for α = 40°, and t = 100, 45 and 15 nm, H K ⋍ 15 , 30 and 150 Oe, respectively. We analyzed two possible contributions to this effect: the shape anisotropy and the magnetocrystalline anisotropy (texture). At low film thicknesses the former becomes dominant. In order to understand the effect of oblique incidence on the in-plane easy axis location we studied the polar plot of reduced remanence m r as a function of both the angle α (between the surface normal and the vapor beam) and the angle γ (between the in-plane applied field and the normal to the incidence plane of atoms during deposition). The behavior of m r ( α , γ ) for α = 10° and 70° is reminiscent of that predicted by the coherent-rotation Stoner and Wohlfarth model, although fallback processes are observed. We found that the films tend to be magnetically isotropic for α = 60°, whereas they are highly anisotropic for α = 10°.


Journal of Magnetism and Magnetic Materials | 1993

Magnetic coupling in YCo2/(Mo)/GdCo2 amorphous sandwiches evidenced by Kerr effect

J.M. Alameda; L.T. Baczewski; N. Bobillo; D. Givord; G.T. Pérez; F.H. Salas

Abstract Magnetic properties of YCo 2 /(Mo)/GdCo 2 amorphous sandwiches, in which the thickness of individual YCo and GdCo layers was 100 nm, were studied. Three cases were considered, viz., YCo/GdCo bilayers and YCo/Mo/GdCo sandwiches where the thickness of Mo was either 50 nm or close to 2 nm. Magnetic coupling effects were analyzed by transverse biased initial susceptibility measurements.


Journal of Magnetism and Magnetic Materials | 1993

Magnetic and magneto-optical properties of NdFeB/Mo and NdFeB/FeB amorphous bilayers

F.H. Salas; C. Dehesa; G.T. Pérez; J.M. Alameda

Abstract Magnetic and magneto-optical properties of NdFeB/Mo and NdFeB/FeB amorphous bilayers, grown by dc triode sputtering on cooled glass substrates, were studied. Transverse Kerr effect, transverse biased initial susceptibility and SQUID magnetometry measurements were performed. Glass/film interface effects, regarding magnetization and anisotropies (dead layers, isotropic sublayers), were found in NdFeB films.


Journal of Magnetism and Magnetic Materials | 1995

Magneto-optics applied to the analysis of magnetization processes in amorphorus ferri/ferro magnetic bilayers

J.M. Alameda; F.H. Salas; G.T. Pérez; L.M. Álvarez-Prado; R. Morales

Abstract We study the magnetization processes in the amorphous ferri—ferro magnetic bilayer of GdCo 2 /YCo 2 by means of the transverse magneto-optic Kerr effect (MOKE). The cycles M cos θ − M sin θ (θ refers to the angle between the magnetization M and the applied field H ) indicate that the irreversible magnetization processes arising at both the coercivity and the transition field do not occur by a coherent-rotation mechanism. MOKE allows one to follow the creation and the extinction of Bloch walls in the bilayer as a function of the applied field. First-order magnetization processes are observed in this macroscopic ferrimagnet when H is applied perpendicularly to the in-plane easy axis of uniaxial anisotropy. In fact, sharp transitions in the magnetic-moment structure are observed at H = 8.5 Oe and H = 17 Oe.


Journal of Magnetism and Magnetic Materials | 1991

Evidence of different magnetic phases in amorphous FexSi1−x/Si multilayers

G.T. Pérez; J.F. Fuertes; J.M. Alameda; F.H. Salas

Abstract Some of the magnetic properties of sputtered amorphous Fe x Si 1− x /Si multilayers are reported. The composition and modulation length range between 0.60 ⩽ x ⩽ 0.80 and 3 A d


Journal of Magnetism and Magnetic Materials | 1999

Periodical magnetic effects in FexSi1−x/Si multilayers, depending upon the modulation length

G.T. Pérez; F.H. Salas; R. Morales; L.M. Álvarez-Prado; J.M. Alameda

Magnetic properties of compositionally modulated Fe x Si 1-x /Si amorphous and crystalline multilayers are reported. From SQUID magnetometry and transverse magneto-optic Kerr effect measurements, we detected noticeable λ-related structure in both magnetization and relative reflectivity. A systematic oscillation is found for λ < 16 A. On the contrary, in samples with definite multilayered structure (λ ≥ 16 A), a significant reduction in magnetization is found as λ decreases.


Journal of Magnetism and Magnetic Materials | 1999

Influence of the film inhomogeneity on local magnetization processes in amorphous thin films having perpendicular anisotropy

R. Morales; G.T. Pérez; J.M. Alameda

Abstract Thin films prepared by co-sputtering present slight inhomogeneities in composition and thickness. In this work we analyze the effect of this lack of uniformity on local magnetization processes in amorphous thin films (Fe x Si 1 − x ) having perpendicular anisotropy. Local magnetization processes have been studied by transverse Kerr effect. Variations in the coercive field H c -suggest that the reversal of magnetization occurs locally.


Physical Review B | 1997

Perpendicular anisotropy detected by transversely biased initial susceptibility via the magneto-optic Kerr effect in Fe x Si 1 − x thin films and Fe x Si 1 − x / Si multilayers: Theory and experiment

L.M. Álvarez-Prado; G.T. Pérez; R. Morales; F.H. Salas; J.M. Alameda


Journal De Physique Iv | 1998

Thermal evolution of magnetic properties of thin films having perpendicular anisotropy

R. Morales; L.M. Álvarez-Prado; G.T. Pérez; F.H. Salas; J.M. Alameda


Journal De Physique Iv | 1998

Coupling of YCo2 thin films in a macroscopic ferrimagnet

F.H. Salas; J.M. Alameda; R. Morales; L.M. Álvarez-Prado; G.T. Pérez

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L.T. Baczewski

Polish Academy of Sciences

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D. Givord

Centre national de la recherche scientifique

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