Thickness Of Soft Magnetic Layer Research Articles

Regulating interfacial exchange coupling in perpendicular magnetized Fe/DO22-Mn3Ga bilayer films

Manganese gallium alloy with DO22-type chemical ordering (DO22-Mn3Ga) thin film represents an intriguing candidate for fabricating the fundamental composition of magnetic devices. In this paper, we prepare the Fe/DO22-Mn3Ga composite films on thermal MgO (100) substrates with different annealing temperatures and report the interfacial exchange coupling between Fe and DO22-Mn3Ga bilayers. Fe layer thickness and annealing temperature are predominant in regulating the nature and strength of interfacial exchange coupling. It is found that there is a ferromagnetic coupling between Fe and DO22-Mn3Ga layers. Their exchange coupling strength can be regulated by changing the Fe soft magnetic layer thickness in a reasonable range. Additionally, the interface diffusion generated from heat treatment induces to change of the nature of exchange coupling. It is possible that Fe replaces Mn site in the DO22-Mn3Ga unit cell due to smaller atomic radius and higher electronegativity compared with Mn. Antiferromagnetic coupling from annealed Fe/DO22-Mn3Ga film with high perpendicular magnetic anisotropy is technologically important to research synthetic antiferromagnetic structure for spin-transfer-torque magnetoresistive random access memory. Our works is helpful for the exploration of interfacial science and development of magnetic devices.

Structural and magnetic properties of L10-FePt/Fe exchange coupled nano-composite thin films with high energy product

Nanoparticle-FePt/Fe bilayer thin films with different Fe layer thicknesses and [nanoparticle-FePt/Fe]n multilayer thin films with various periods were fabricated by DC magnetron sputtering. Their structures and magnetic properties (energy product and exchange coupling) were investigated by X-ray diffraction technique and vibrating sample magnetometer, respectively. The results show that coercivities of FePt/Fe bilayer films are dropped from 10.7kOe to 0.53kOe with increasing Fe soft magnetic layer thickness, due to the interconnecting of FePt nano-particles by Fe-rich soft magnetic phase and decreasing of the ordering degree of L10-FePt phase. The critical Fe layer thickness changing the annealed film from granular to continuous microstructure is about 4nm. For multilayer [FePt/Fe]n films, both ordering degree of L10-FePt phase and magnetic properties are improved with the number of layer periods. Moreover, a maximum energy products as high as 21.65MGOe is obtained in the [FePt/Fe]5 multilayer film. The enhancement of saturation magnetization and energy products can be ascribed to the high ordering degree of FePt phase as well as the strong exchange coupling among L10-FePt hard magnetic phase and Fe-rich soft magnetic phase.

Structural and magnetic properties of L10/A1, FePt nanocomposites

In this work structural and magnetic properties of (L10-FePt/A1-FePt) exchange coupled nanocomposites are presented. Semi spherical “dome-like” nanocomposites with L10 FePt isolated nanoparticles and A1 FePt (fcc) cap layers were obtained by depositing A1-FePt on type L10 FePt nanoparticles in order to understand the influence of the soft magnetic layer thickness on the magnetic properties of the system. Epitaxial growth is confirmed by X-ray diffraction and TEM, while the coercivity decreases dramatically for the L10/A1-FePt system when the thickness of the A1-FePt cap layers is increased. This result can be used to realize ultrahigh magnetic recording media with tunable coercivity, suitable for conventional write heads.

Magnetic Properties of Anisotropic Pr–Fe–B/Fe/Pr–Fe–B Films

Pr-Fe-B/Fe/Pr-Fe-B films with different Fe layer thicknesses were deposited by magnetron sputtering on Si (100) substrate heated at 650 degrees C. Structural and magnetic properties of the Pr-Fe-B/Fe/Pr-Fe-B films were investigated. X-ray diffraction and magnetic measurement results reveal that the Pr-Fe-B/Fe/Pr-Fe-B films are anisotropic when the thickness of Fe layer is smaller than 50 nm. The enhancement of the saturation magnetization in nanocomposite films is attributed to the exchange coupling between the soft and hard phases. The highest coercivity of about 13.9 kOe is achieved in the Mo(50 nm)/Pr-Fe-B(50 nm)/Mo(2 nm)/Fe(2 nm)/Mo(2 nm)/Pr-Fe-B(50 nm)/Mo(50 nm) film and increasing the thickness of soft-magnetic layer results in a continuous decreasing of the coercivity.

Coercivity variation in exchange-coupled Fe/FePt bilayer with perpendicular magnetization

The soft/hard Fe/FePt film with perpendicular magnetization has been deposited on a glass substrate. The (001) oriented L1 0 FePt film was obtained when annealed by rapid thermal process at 800 °C and a Fe layer was deposited at room temperature with thicknesses of 2 nm to 20 nm. Controlling the Fe layer thickness allowed modification of the hysteresis loops from out-of-plane rigid magnet to in-plane exchange-spring like magnet due to the nanometer scale interface coupling. When the Fe layer thickness increased to 2 nm, the out-of-plane coercivity is reduced to 5.9 kOe but the remanence ratio (0.98) is still high. The Fe (2 nm)/FePt film shows perpendicular magnetization with linear in-plane hysteresis loop. The remanence ratio is reduced to 0.85 when the Fe layer thickness increased to 5 nm. When the Fe layer thickness was varied up to 10–20 nm, the in-plane hysteresis loop shows exchange-spring like behavior with two-step magnetization reversal processes. The films with perpendicular coercivity were moderated by the thickness of soft magnetic layer.

Coercivity of ledge-type L1-FePt/Fe nanocomposites with perpendicular magnetization

Exchange-coupled ledge-type L10-FePt/Fe composite systems with out-of-plane anisotropy composed of nanostructured L10-FePt films covered by Fe are prepared to analyze the influence of the soft magnetic layer thickness on the magnetic properties. By the soft magnetic layer thickness dFe the coercivity can be tailored according to a 1/dFe1.38 relation. This result can be used to realize recording media with coercivities in the range which are afforded by conventional write heads.

Magnetic Properties of Exchange-Coupled L1$_{0}$-FePt/Fe Composite Elements

Exchange-coupled L10 -FePt/Fe composite systems with out-of-plane anisotropy are produced to study the influence of the soft magnetic layer thickness and of the character of the interface between hard magnetic L10-FePt and soft magnetic Fe on the magnetic properties. By the soft magnetic layer thickness d Fe the coercivity can be tailored according to a 1/d Fe 2 relation. By depositing part of the Fe layer at elevated temperatures a graded interface between the L10-FePt layer and the Fe layer is formed which allows an additional fine tuning of the coercivity. This behavior is confirmed by micromagnetic numerical simulations. The simulations furthermore show that the reversal behavior and the thermal stability are nearly the same for out-of-plane and in-plane anisotropy of L10-FePt. If the remanent magnetization configuration shows deviations from the homogeneous magnetization distribution an alternative low-field thermal reversal mode occurs.

Dependence of GMR on NiFe layer thickness in high sensitive simple spin valve

The dependence of the giant magnetoresistance on Ni/sub 81/Fe/sub 19/ soft magnetic layer thickness is investigated experimentally for a simple spin valve with a top-pinned structure of Ta (6 nm)/Ni/sub 81/Fe/sub 19//Co/sub 90/Fe/sub 10/ (1 nm)/Cu (1.8 nm)/Co/sub 90/Fe/sub 10/ (3.5 nm)/Ir/sub 20/Mn/sub 80/ (8 nm)/Ta (6 nm). With Ni/sub 81/Fe/sub 19/ thickness increased from 6 nm to 7 nm, the magnetoresistance (MR) ratio decreases sharply from 8.34% to 3.34%, whereas it changes only slightly within the thickness ranges from 2-6 nm and from 7-12 nm, and larger MR ratios are obtained in the range from 2-6 nm. For a spin valve with an optimized thickness of Ir/sub 20/Mn/sub 80/ (11 nm) and top Ta (3 nm), the MR dependence is in accordance with the former structure when Ni/sub 81/Fe/sub 19/ thickness changes from 3.5 to 5.5 nm, and an optimized spin valve with 4.5-nm-thick Ni/sub 81/Fe/sub 19/ is obtained. This spin valve has a large MR ratio (9.15%), low coercive force (0.85 Oe), and high sensitivity, which makes it promising for applications.

Reversible magnetization processes and energy density product in Sm–CoFe and Sm–Co/Co bilayers

The hysteresis properties of epitaxial SmCo/Co and SmCo/Fe bilayers are calculated by the solution of the Landau–Lifshitz Gilbert equation. The thin film grain structure is taken into account using appropriate finite element techniques. The J(H) curve shows the typical exchange spring behavior for the bilayer if the soft magnetic layer thickness exceeds 10 nm. However, the reversible rotations of the magnetization for low external field deteriorate the maximum energy density product. Straight B(H) curves are obtained only for a Fe layer thickness of 5 nm. Magnetization reversal starts with the reversible rotation of the soft layer magnetization. Initially, the magnetization rotates in opposite directions in different regions of the film. The reversible rotations penetrate substantially into the hard layer.

Magnetic Properties of Nanostructured SmCo/FeCo Multilayers

The dependence of reduced remanence (Mr/Ms) and coercivity of Sm22Co78/Fe65Co35 bilayer and Sm22Co78/Fe65Co35/Sm22Co78 triple-layer films on Fe65Co35 soft-magnetic layer thickness d, was systematically investigated. All the hysteresis loops of the films exhibited a single-phase behavior, reflecting a strong exchange coupling between soft-and hard-magnetic phase. Mr/Ms showed a monotonic increase with increasing Fe65Co35 thickness d, and the coercivity would show a peak with increasing d. From the plot of M versus applied field H, it is shown that the positive profile decreases and the negative interaction profile increases with the increase of interfaces between soft-and hard-layers.