A.D. Santos

DOMAINS AND GIANT MAGNETO-IMPEDANCE IN AMORPHOUS RIBBONS BY MAGNETO-OPTICAL KERR EFFECT

By longitudinal magneto‐optical Kerr effect microscopy we analyzed the development of the domain structure in Co70.4Fe4.6Si15B10 amorphous ribbons for which giant magneto‐impedance had been observed. Using transverse and longitudinal magneto‐optical Kerr effect magnetometry we measured the magnetization direction around the hysteresis loop. These results allowed us to model the domain structure of the sample during the giant magneto‐impedance measurements.

Structural and Magnetic Study of FePt Thin Films as a Function of the Deposition Temperature

The structural and magnetic properties of polycrystalline FePt thin films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). The alloys were prepared by dc magnetron sputtering on oxidized silicon substrates with a Pt buffer layer at substrate temperatures (T s ) varying from 300 to 600 °C. XRD measurements show that the increase of T s enhances the degree of crystalline ordering and also the crystallographic grain size. A face centered cubic crystalline structure with (111) texture is observed. AFM images reveal the presence of a granular structure. The morphological grain size increases with the increase of T s . In-plane and out-of-plane hysteresis measurements, using VSM, show that the saturation magnetization M s decreases with increasing T s . The coercivity increases abruptly from 1.3 to 6.0 kOe, in the in-plane geometry, and from 1.6 to 5.6 kOe, in the out-of-plane geometry, when T s varies from 450 to 500 °C.

Magnetic characterisation and X-ray magnetic circular dichroism study of amorphous YCo2 films

Abstract In this work, we analyse the role of Y in the magnetic behaviour of amorphous YCo2 films. The effect of the deposition conditions, such as argon pressure used during film production, was verified. The increases observed in the Co magnetic moment and in Curie temperature TC were attributed to a reduction of the film density with the increase of the argon pressure. Magnetic (SQUID) and magneto-optical (TMOKE) measurements were performed in order to show that Y does not contribute to the magnetic moment of the amorphous YCo2 film. This was also verified using X-ray magnetic circular dichroism (XMCD) measurements at the Y L2,3-edges.

X-ray absorption spectroscopy study of FePt thin films

Equiatomic FePt thin films with fcc or L10 structure were studied by x-ray-absorption spectroscopy. The extended x-ray-absorption fine structure and x-ray-absorption near edge structure analysis, sensitive to the local structure and chemical order, show the formation of a Fe-rich neighborhood around Fe, indicating segregation of atomic species inside the film, and not a random distribution, as pointed out in the literature. The polarization dependence of the extended x-ray-absorption fine structure signal reveals and quantifies the different chemical and local order inside the samples, for both kinds of structure. The results are correlated with the long-range structural order measured by x-ray diffraction and magnetic properties of the material.

Figure of merit for transverse magneto-optical Kerr effect

Abstract An expression for the Fresnel coefficient r pp is established in the general case of an interface between two semi-infinite media and is extended to multilayers. By analogy with the well-known Θ K R for polar Kerr effect, a figure of merit is proposed for the transverse geometry. It is an alternative characterizing quantity to the relative change of reflectivity for p polarization, Δ R p / R p .

Temperature dependence of the macroscopic ferri–ferromagnetic transition in amorphous Y–Co/Gd–Co bilayers

We studied the temperature dependence of the macroscopic ferri–ferromagnetic transition in amorphous Y–Co/Gd–Co bilayers. The samples were produced by sputtering, and characterized by vibrating sample magnetometer and transverse magneto-optical Kerr effect at low temperature. From a model of the unusual shaped domain wall (DW) at the interface of the bilayer, we determined the temperature dependence of the thickness δ and relative position Δ of the DW and, also the exchange constant A.

The macroscopic ferri‐ferromagnetic transition in amorphous Y–Co/Gd–Co bilayers

We developed a model to completely explain the domain wall existing at the interface of an amorphous Y–Co/Gd–Co bilayer. Samples produced by sputtering, were characterized by Rutherford backscattering spectrometry and transverse magneto‐optical Kerr effect. From the experimental parameters we determined the thickness (δ) and relative position (Δ) of the domain wall, and also the exchange constant (A) for the Co–Co atom pair. The room temperature value of A was found to be (4.8±1.4)×10−8 erg/cm.

Depth-dependent chemical and magnetic local orders in thin magnetic films

The authors report on the use of x-ray absorption spectroscopy with resolved grazing incidence to clarify the thickness-dependent magnetic properties in nanometric CoPt films. They show that in the thinnest samples the chemical order that induces the perpendicular magnetic anisotropy has no depth dependence. However, in the thicker samples the chemical order is depth dependent along the film thickness, with a disordered layer close to the substrate. The ability of the experimental approach to address the depth dependence of the local structural parameters makes it a unique tool, suitable for nanometric structure where this dependence is an important problem.

T131. INCIDENCE OF FIRST-EPISODE PSYCHOSIS IN THE CATCHMENT AREA OF RIBEIRÃO PRETO, BRAZIL

Abstract Background In the study “Schizophrenia and Other Psychoses Translational Research: Environment and Molecular Biology” (STREAM), we estimated the incidence of first-episode psychosis (FEP) in the catchment area of Ribeirão Preto, Brazil, and investigated the role of environmental and biological factors in the aetiology of the psychoses. STREAM is part of the international consortium “European Network of National Schizophrenia Networks Studying Gene-Environment Interactions” (EU-GEI).1 Here, we describe the incidence of FEP in this Brazilian catchment area according to some demographic characteristics of the population. Methods Twenty-six counties compose the catchment area under study. Ribeirão Preto is the main city of the region, with a population of 604,682 inhabitants, population density of 929.8 inhabitants/Km2, per capita gross intern product (GIP) of U

Depth dependent local structures in thin films unraveled by grazing incidence x-ray absorption spectroscopy

9,143,20 and human development index (HDI) of 0.800, ranked 40th among 5,570 Brazilian municipalities. The population of the remaining 25 counties varied from 1,953 to 110,074 inhabitants (median=23,862), median population density of 75.0 inhabitants/Km2 (interval 13.2–308.4 inhabitants/ Km2), median GIP of U