Papers by Keyword: Magnetic Thin Film

Abstract: Ni, permalloy (Py: Ni - 20 at. % Fe), and Co films of 40 nm thickness are prepared on GaAs (100) single-crystal substrates at room temperature and 200 °C by magnetron sputtering. The growth behavior and crystallographic properties are studied. In early stages of film growth, metastable bcc single-crystals nucleate on the substrates for all the film materials. The crystal structure is stabilized through hetero-epitaxial growth. With increasing the thickness beyond 2 nm, the bcc structure starts to transform into fcc or hcp structure through atomic displacements parallel to the bcc {110} close-packed planes. The transformation orientation relationships are fcc {111}<10>, hcp {0001}<110> || bcc {110}<001>. The resulting Ni and Py films consist of a mixture of bcc and fcc phases, whereas the Co films involve an hcp phase in addition to the metastable bcc phase.

Abstract: Arrays of SU-8 photoresist pillars (10 μm ×10 μm × 50 μm) on copper substrates were fabricated by X-ray lithography. The photoresist-coated substrates were irradiated by X-ray from a synchrotron source through patterned silver dots on a graphite mask. After the resist development, the chemically stable and mechanically hardened SU-8 pillars exhibited smooth vertical sidewalls and cross section with up to 10 % dimensional errors from the designated pattern. Cobalt of thickness ranging from 50 to 80 nm was then deposited on these patterned substrates by RF sputtering. These cobalt films on SU-8 pillars showed a lower in-plane magnetization than that of continuous cobalt films because of their smaller grain size. The measurement with out-of-plane magnetic field gave rise to a higher magnetization and this anisotropic behavior was observed only in cobalt-coated pillars.

Abstract: This paper reports on the effect of Sm doping concentration on structural and static magnetic properties of electrodeposited NiFe thin films. A reduction of Ni concentration from 80 to 50 percent was observed as the Sm concentration increased from 0 to 25%. XRD analyses revealed that a transition from crystalline to partially disordered state occurred on the Sm-doped NiFe thin films and ultimately transformed to amorphous state at higher concentration. The saturation magnetization decreased to ~50% at 25% Sm doping as compared to that of NiFe thin films.

Abstract: The paper describes results of investigation on sputtered NiFe Films to determine the sputter deposition condition that could produce magnetic field sensors with the desired magnetic and magnetoresistive properties. The magnetic thin films materials used in such devices should have a low coercive force, a low anisotropy field and low magnetization dispersion, α50 with high magnetoresistance ratio. From the results presented, it is shown that that the most useful films for 82%Ni-Fe composition are produced at 200 °C-250 °C moderate substrate temperatures. It is also possible to specify the substrate bias potential and sputter gas pressure sputter deposition conditions under which the 82%Ni-Fe thin films may be employed for the production of magnetoresistine sensors with near optimum magnetic and magnetoresistive properties. The work also provide understanding of the effects on the magnetic properties of sputtered magnetic films that is very limited as current literature is almost entirely limited to evaporated magnetic films.

Abstract: In this article, we review our recent research on Fe3O4 epitaxial thin films and Fe3O4/MgO/Fe epitaxial heterostructures. More specifically, we report on the magnetotransport properties of Fe3O4 epitaxial films in a wide range of film thicknesses and temperatures, focusing on the anomalous, planar and ordinary Hall effects. We also summarize our insight on the origin of the enhanced magnetic moment found in ultra-thin magnetite films (thickness t < 5 nm). Finally, our work on the growth, and structural and magnetic characterization of heteroepitaxial Fe3O4/MgO/Fe trilayers is presented.

Abstract: The paper describes results of investigation on sputtered NiFe Films to determine the sputter deposition condition that could produce magnetic field sensors with the desired magnetic properties. The magnetic materials used in such devices should have a low coercive force, a low anisotropy field and a low magnetization dispersion, α50. .The results of systematic investigation of radio-frequency (RF) sputtered, RF biased, 82-18 % NiFe films showed (i) Improved Kobelev methods were applied to magneto-optic measurement techniques, suppress the magnetization ripples when subjected under the application of dc field. (ii) Anisotropy field results indicated an inverse trend with increasing substrate temperature (iii) the experimental measurements on magnetization dispersion relatively constant up to 200 °C with α50 approximately 1.2°, it then increases more sharply to about 3.5° at 400 °C substrate temperature. The work also provide understanding of the effects on the magnetic properties of sputtered magnetic films that is very limited as current literature is almost entirely limited to evaporated magnetic films.

Abstract: The elemental magnetic moments of Co and Cr in CoCrPt films were investigated using xray magnetic circular dichroism (XMCD). The spin and orbital moments of Co was calculated using the sum rules; it was found that the magnetic moment of Co in CoCrPt films was dominated by spin moment contribution. The total magnetic moment of Co was found to be lower than that of bulk Co. Further, the Cr moment was aligned anti-ferromagnetically with respect to Co, resulting in a decrease of saturation magnetization (Ms) in CoCrPt films.