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In this investigation, the changes of magnetic properties with thermal ageing of \Fe3{\Ni} alloy have been measured. The changes in coercivity and Barkhausen noise were measured, and the results have been interpreted as magnetic ordering, based on the neuron diffraction results. The \Fe3{\Ni} alloy forms ordered superstructures, and the investigation gives the information concerning the effect of atomic ordering on the magnetic structure. The neutron diffraction results shows that the superlattice peaks correspond to a simple cubic lattice, and the intensity increases with increasing ageing time. In the ordered state, the intensity of super lattice shows inverse trends with (1 1 1) fcc peak, which means that disordered states transformed to ordered states with thermal ageing. [ABSTRACT FROM AUTHOR]

We report the magnetism of a ferromagnetic two phase mixture system by investigating the microstructural evolution and relevant property changes as a function of alloy composition in CoFeSiB film. The crystal structure evolved from an amorphous to hcp Co nanocrystal embedded two-phase mixture when Co concentration exceeded the critical amount (~75 at.%) confirmed through TEM and XRD. Very low coercivity value was observed in the amorphous samples. The soft magnetic properties are due to the fact that the magnetic moments of Co-rich phase are exchange-coupled via the amorphous matrix, as a consequence the magnetic anisotropies are averaged out in the amorphous system. Meanwhile, beyond 75 at. % of Co, an abrupt increase in coercivity was observed in the nanocrystalline samples where highly anisotropic Co nanocrystals were precipitated. The hard magnetic properties resulted from the magnetic decoupling (breaking of the nanocrystal-amorphous matrix-nanocrystal coupling chain) because the exchange forces are not able to overcome the magnetocrystaline anisotropy. We also found that antiferromagnetic exchange coupling existed at the nanocrystal-amorphous matrix interfaces. [ABSTRACT FROM AUTHOR]

The dependencies of the stack number N on perpendicular exchange-biasing (Hex) and coercivity Hc) in [Pd/Co]N and [Pd/Co (or CoFe)]N/FeMn multilayers were investigated. With the help of the careful designs of layer structures, a series of samples whose surface anisotropies have the linear function N was prepared with constant bulk anisotropies. From the experimental data obtained, it was found that Hex does not depend on the surface anisotropy, while Hc shows a strong dependence. Therefore, it is possible to tailor wide ranges of Hc (300–600 Oe) without varying Hex (∼200 Oe) through the single control parameter stack number N. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs), which consisted of amorphous CoFeSiB layers, were investigated. The CoFeSiB layers were used to substitute for the traditionally used CoFe and/or NiFe layers with an emphasis given on understanding the effect of the amorphous free layer on the switching characteristics of the MTJs. CoFeSiB has a lower saturation magnetization (Ms : 560 emu/cm³) and a higher anisotropy constant (Ku : 2 800 erg/cm³) than CoFe and NiFe, respectively. An exchange coupling energy (Jex) of -0.003 erg/cm² was observed by inserting a 1.0 nm Ru layer in between CoFeSiB layers. In the Si-SiO2-Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlOx/CoFeSiB 7 or CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60 (in nanometers) MTJs structure, it was found that the size dependence of the switching field originated in the lower Jex using the experimental and simulation results. The CoFeSiB synthetic antiferromagnet structures were proved to be beneficial for the switching characteristics such as reducing the coercivity (Hc) and increasing the sensitivity in micrometer size, even in submicrometer sized elements. [ABSTRACT FROM AUTHOR]