Academic literature on the topic 'Samarium Cobalt Magnetic Thin Films'

This report describes the growth and characterization of thin amorphous samarium-cobalt alloy films. The samarium-cobalt alloy was grown by DC magnetron sputtering in the presence of an external magnetic field parallel to the thin film. The external magnetic field induces a uniaxial in-plane magnetic anisotropy in the samarium-cobalt alloy. The thin films were characterized with x-ray scattering, and the magnetic anisotropy was characterized with the magneto optic Kerr effect. The measurements showed a uniaxial in-plane magnetic anisotropy in the samarium-cobalt alloy films. It is not clear how amorphous the samples really are, but there are indications of crystalline and amorphous areas in the alloys.

Made available in DSpace on 2014-10-09T12:45:30Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T13:56:26Z (GMT). No. of bitstreams: 1 07175.pdf: 4800774 bytes, checksum: 7591ed2b66c61d81600006d10b99afb7 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The goal of this thesis is to study the microstrucutre and texture of Yttrium-Nickel- Borocarbide and Samarium-Cobalt thin film heterostructures prepared by Pulsed Laser Deposition and to establish structure-property relations for these materials in order to improve their properties and design new structures. Coincidence site lattice epitaxy was explored in most of these heterostructures (substrate, buffer and film) and studied in detail for each case. Epitaxial thin films of the superconducting borocarbide compound YNi2B2C were grown on single crystal MgO (100) substrates without and with Y2O3 buffer layer using pulsed laser deposition (PLD). In both cases YNi2B2C grows with [001] normal to the substrate. However, the in-plane texture depends on the starting condition. For samples without buffer layer, oxygen from the substrate diffuses into the film and forms an Y2O3 reaction layer at the interface. As a consequence, a deficiency of Y is generated giving rise to the formation of secondary phases. On the other hand, using an artificial Y2O3 buffer layer secondary phases are suppressed. The texture of the Y2O3 layers determines the texture of the YNi2B2C film. The superconducting properties of the borocarbide films are discussed with respect to texture and phase purity. To prevent the formation of an impurity phase at the interface, it was the aim of this preliminary investigation to study YNi2B2C films deposited onto single crystal MgO (100) substrates with an Ir buffer layer. The Ir buffer layer shows a strong cube-on-cube texture onto MgO(100) and also prevents the formation of an Y2O3 interlayer. However, during deposition of YNi2B2C the buffer layer disappears by Ir diffusion into the borocarbide film. The YNi2B2C film exhibits a c-axis texture consisting of four components. As a consequence of these effects, the superconducting transition Tc90 equals up to 13K, but with a transition width of 4K. In the second part of this work, hard magnetic Sm-Co/Cr films were epitaxially grown on MgO(100) and (110) substrates. They were characterized by X-ray pole figure measurements and transmission electron microscopy. For films deposited on MgO(100) at 700ºC, orientations are found with the c-axis aligned in-plane and out-of-plane. By lowering the deposition temperature to 370ºC, the out-of-plane orientations disappeared. Further lowering to 350ºC leads to the formation of amorphous regions in the SmCo5 film. For films grown on MgO(110) the Cr buffer deposition temperature plays an important role. When deposited at 700°C Cr(211) and (100) growth is observed leading to two different types of SmCo5 in-plane orientations. By lowering the Cr-buffer deposition temperature to 300ºC only one buffer and one SmCo5 orientation exists: Cr(-211)[0-11] and SmCo5(10-10)[0001]. The exact orientation relationships between substrate, buffer and films are explained and their correlation with magnetic properties are discussed.

The magnetic recording media used for hard disks in laptops and PC's is constantly being improved, leading to rapid increases in data rate and storage density. However, by the year 2010, it is predicted that the superparamagnetic limit will be reached, which is potentially insufficient for data storage. At the beginning of this century, CoCr -based alloys are used in longitudinal media since cobalt has a high magnetocrystalline anisotropy. In this thesis, the static and dynamic properties of longitudinal recording thin films were investigated in order to explain and correlate their magnetic characteristics to their recording properties. The samples in question were test samples and some were in commercial use. Magnetic techniques such as high field ferromagnetic resonance and torque magnetometry were used to determine accurately the crystalline anisotropy field. High field ferromagnetic resonance is an ideal tool to determine the crystalline anisotropy, magnetisation, Lande g-factor and the gyromagnetic damping factor. In contrast to previous work, there are no FMR simulations and so all the relevant parameters were determined directly from measurement. Ideally, there should be no exchange interactions between the neighbouring cobalt grains; however, interactions between the grains within the CoCr-alloy recording layer exist. Previous work on the measurements of interactions in recording media involves measuring the sample's magnetisation. In this thesis, an alternative novel method involves torque magnetometry. Another technique that was used in this thesis is small angle neutron scattering, which aims to determine the size of the magnetic grains and compare that with the physical size determined from TEM, by Seagate. There is an extended section on CoxAg1-x granular thin films, which involves determining the sample's g-factor, effective anisotropy, grain size, exchange constant and comparing the FMR lineshapes at 9.5 and 92GHz.

In situ polar Kerr effect measurements have been used to study the magnetic anisotropy of Au(111)/Co/X, Pd(111)/Co/X, Cu(111)/Co/X, and Pd(100)/Co/X sandwiches, where X is the nonmagnetic metal Ag, Au, Cu, Ir, and Pd or the insulator MgO. The films were grown by molecular beam epitaxy (MBE). For the metals, we found that the magnitude of the Co/X perpendicular interface anisotropy is strongly peaked at ∼1 atomic layer (1.5-2.5 Å) coverage. To investigate structural influences on the anisotropy, we have used reflection high energy diffraction (RHEED) and low energy electron diffraction (LEED) to measure changes resulting from overlayer coverage. Analysis of digitized RHEED images captured every ∼1 Å during metal overlayer coverage shows no abrupt change of the in-plane lattice constant. We have also investigated the out-of-plane lattice spacing as a function of nonmagnetic metal coverage by measuring LEED I-V curves along the (0,0) rod. In the case of Cu, where the LEED behavior is nearly kinematic, we see no evidence of any abrupt structural changes at ∼1 atomic layer coverage. These results suggest the observed peak in magnetic anisotropy is not structural in origin. The influence of an insulating overlayer, MgO, on the perpendicular magnetic properties was also investigated.

Structural, magnetic, and magneto-optical properties of Co/Pd and Co/Pd/Cu superlattices, ultra-thin Co films and MnSb alloys have been studied. The superlattices and Co films were grown by molecular beam epitaxy (MBE) while the MnSb alloy films were made by sputtering techniques. Several x-ray diffraction techniques were used to analyze the physical structure of the superlattices and alloys. Magnetometry techniques were used to determine some of the room temperature and temperature dependent magnetic properties of the films. In situ and ex situ measurements of the magneto-optical properties of the ultra-thin Co films and alloys also were made.

Thin films (5nm ± 2nm thick) of ZrO2, Al2O3, TiO2, Sm, Gd, Zr, Ni, and Pt were deposited onto TbFeCo films (100nm ± 20nm thick) on silicon and graphite substrates and analyzed with XPS as prospective candidates for TbFeCo diffusion barriers. Metals were chosen primarily according to electronegativity. Samples were typically heated to 272°C in UHV for 20 hours to enhance diffusion. Experiments with the metals were performed in a more consistent manner than with the oxides. The Sm, Gd, and Zr were reactively oxidized during the deposition. The Sm/Sm-oxide and Gd/Gd-oxide appeared to be favorable candidates for TbFeCo diffusion barriers. TbFeCo was not detected near the surface before or after heating the samples to 272°C for 20 hours and depth profiles indicated oxygen contamination decreased steadily as the barrier/TbFeCo interface was approached. For the other materials examined, either the oxides were reduced (at least partially) during heating to 272°C (381°C for Al₂O₃) or diffusion of TbFeCo was detected after heating, indicating that they would not be favorable candidates for TbFeCo diffusion barriers.