Search

The laminated soft layer (LSL) that comprises the granular [CoPtCr–SiO2/Pt]N multilayers with perpendicular magnetization is designed to reduce the switching field of exchange coupled composite (ECC) media. The magnetic simulation shows that the reduction in the switching field can be optimized by changing the coupling strength between the adjacent CoPtCr–SiO2 layers in LSL. The reversal mechanism of ECC media with LSL depends on the bilayers number N of [CoPtCr–SiO2/Pt]N. Both simulation and experiments reveal that the domain-wall assisting reversal strongly depends on the thickness of LSL. By properly adjusting the coupling strength inside the LSL, the switching and saturation fields can be significantly reduced at a limited thickness of the soft layer due to decreased domain-wall length by the Pt lamination. [ABSTRACT FROM AUTHOR]

We investigated the reorientation of exchange anisotropy in the epitaxial (002) IrMn/CoFe bilayers. Transitions of exchange-bias field from a negative field to a positive field with increasing time scale were observed at room temperature. The negatively magnetized state combining with the strong magnetocrystalline anisotropy of CoFe may raise the probability that the interfacial spins of thin IrMn layers were thermally relaxed to the direction of CoFe magnetization; therefore, after a period of time, the exchange-bias direction was reversed. This process can be further enhanced when samples were placed under the setting field. The double-shifted magnetization curve observed in this system was used as a good indicator for the relaxation of interfacial spins of IrMn. [ABSTRACT FROM AUTHOR]

The exchange-bias films of ferrimagnetic/ferrimagnetic, ferromagnetic/ferromagnetic, and ferromagnetic/antiferromagnetic bilayers were fabricated to investigate their interfacial exchange energy Δσ. Δσ of TbFeCo bilayers is larger than 5 erg/cm[SUP2]at room temperature. By varying the composition of TbFeCo layers, both positive and negative exchange bias have been observed. A highly uncompensated-spin interface model was proposed to explain the strong exchange interaction in TbFeCo bilayers. Due to the characteristics of highly uncompensated-spin interface at TbFeCo bilayers, the exchange coupling field in TbFeCo bilayers exhibited less dependence on interfacial roughness than that in IrMn/NiFe bilayers. In addition, by adjusting the composition of TbFeCo, the anisotropy of pinning layer can be manipulated and exhibits strong effects on exchange bias of TbFeCo bilayers. [ABSTRACT FROM AUTHOR]

Single-twin (T)-domain NiO films were obtained by stress induced during the growth, and the exchange anisotropy between NiO and NiFe films was studied by using micromagnetic modeling. The compressive strain along the [111] is -7.16 × 10[sup -4], which forces spins of NiO to lie on the (111) plane parallel to the film surface. The neutron diffraction shows that the moments of NiO predominantly lie in the film plane with random orientations, that is, the NiO is of a single T-domain, and multi-spin-rotation-domains in the film plane. The effective crystalline anisotropy of (111) NiO, calculated from micromagnetic modeling, is 2.4 × 10[sub 4] ergs/cm[sup 3]. The majority of NiO moments at the interface switched along with NiFe moments due to the low effective anisotropy, leading to a large coercivity and a low exchange field. [ABSTRACT FROM AUTHOR]

In-plane magnetic anisotropy was studied in Co films epitaxially grown on NiMn (001) films. The hysteresis loops measured in-plane perpendicular to the exchange field show double shifted loops, and the magnetization of Co to rotate coherently. Magnetic anisotropy constants can be determined from these double shifted loops. Exchange coupling in NiMn/Co not only induces a unidirectional anisotropy but also a uniaxial anisotropy. This induced uniaxial anisotropy may contribute to the enhancement of Co coercivity. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied the variation of perpendicular magnetic anisotropy (PMA) of CoFeB layers with the oxidation degree of the MgO buffer layers. After annealing at 330 °C, the out-of-plane anisotropy field (Hk) of 1.5-nm CoFeB could be optimized to 3.1 kOe. To investigate the orbital hybridization of the Fe-3d and O-2p, the orbital moments per hole (morb/Nh) of Fe in annealed CoFeB layers were extracted by using x-ray magnetic circular dichroism. The dependence of morb/Nh on the oxidation time of MgO coincided with that of Hk, which revealed that PMA of annealed CoFeB originated from the interfacial orbital hybridization. [ABSTRACT FROM AUTHOR]

(001)-oriented FePt graded media are obtained by using PtMn underlayers. The PtMn underlayer not only behaves as the (001) structural template but provides the diffusion source of Mn. The diffusion of Mn into FePt reduces its anisotropy but, on the other hand, the exchange coupling between antiferromagnetic PtMn and ferromagnetic FePt enhances the anisotropy. Hysteresis loops taken from x-ray magnetic circular dichroism confirm the competition between these two effects, leading to the lowest anisotropy in the middle of FePt. [ABSTRACT FROM AUTHOR]

Symmetric and asymmetric double-shifted loops were observed at room temperature in epitaxial (002) Ir20Mn80/Co50Fe50 samples placed in a setting field applied along collinear and noncollinear directions with the deposition-field direction, respectively. A coherent rotation model with extra unidirectional exchange and uniaxial anisotropies induced by the noncollinear setting field is proposed to explain the asymmetric double-shifted loops. Due to the existence of the biaxial magnetocrystalline anisotropy, the noncollinear setting field results in two interfacial Ir20Mn80 spin orientations, where the major spins determine the direction to observe double-shifted loops and the minor spins determine the field-shift and the asymmetry of double-shifted loops. [ABSTRACT FROM AUTHOR]

We demonstrate a simple method to tailor the magnetization reversal mechanisms of Co/Pt multilayers by depositing them onto large area nanoporous anodized alumina (AAO) with various aspect ratios, A=pore depth/diameter. Magnetization reversal in composite (Co/Pt)/AAO films with large A is governed by strong domain-wall pinning, which gradually transforms into a rotation-dominated reversal for samples with smaller A, as investigated by a first-order reversal curve method in conjunction with analysis of the angular dependent switching fields. The change in the magnetization reversal mode is attributed to topographical changes induced by the aspect ratio of the AAO templates. [ABSTRACT FROM AUTHOR]

Co/Pt multilayers deposited on anodized alumina substrates are introduced as percolated perpendicular media. The pores act as pinning sites due to variations of thickness and anisotropy direction around the perimeters. Coercivity, domain size, and switching field can be engineered by controlling pore density. The media exhibit strong perpendicular anisotropy and the switching field remains unchanged at its minimum up to an angular deviation of 50° from the easy axis. A better tolerance of switching-field distributions can thus be achieved, which may help to achieve a high signal-to-noise ratio. The thermal stability of the proposed media is investigated by micromagnetic simulations. [ABSTRACT FROM AUTHOR]

It is demonstrated that the large-area FePt network nanostructures with strong perpendicular anisotropy can be obtained by growing the mask of porous anodic aluminum oxide (AAO) directly on the L10-FePt films and subsequent plasma etching. The aspect ratio of the AAO mask is critical to achieve well-organized FePt networks. The out-of-plane coercivity of FePt networks is enhanced by 20% compared to that of the FePt film, due to the domain wall pinning effects imposed by the presence of pores. [ABSTRACT FROM AUTHOR]

The laminated soft layer (LSL) [Pt/CoPtCr-SiO2]5 was used in exchange coupled composite (ECC) media and exhibited a tunable perpendicular anisotropy by changing the thickness of Pt. By using x-ray magnetic circular dichroism, the incoherent reversal in the ECC media with a LSL was directly observed. The nucleation field of ECC media was found to be dominated by the anisotropy of the LSL. The increased thickness of the Pt layers in the LSL reduced the anisotropy, which promoted incoherent reversal; however, with the Pt thickness increasing larger than 0.9 nm, the interlayer coupling between the LSL and the hard layer was significantly reduced, and thus the assisting effect was suppressed. Furthermore, the dependence of remanent coercivity Hcr on the Pt thickness confirmed that the assisting effect can be optimized by controlling the Pt thickness to balance the LSL anisotropy and the interlayer coupling. [ABSTRACT FROM AUTHOR]

Investigates the effect of microstructure and interface conditions on the anisotropic exchange fields of NiO/NiFe bilayers. Enhancement of the exchange field in the small-grained NiO; Surface roughness and the grain size of NiO on amorphous alumina; Formation of small domains in NiO.

We have achieved (001) oriented L10 (Fe1-xCux)55Pt45 thin films, with magnetic anisotropy up to 3.6 × 107 erg/cm3, using atomic-scale multilayer sputtering and post annealing at 400 °C for 10 s. By fixing the Pt concentration, structure and magnetic properties are systematically tuned by the Cu addition. Increasing Cu content results in an increase in the tetragonal distortion of the L10 phase, significant changes to the film microstructure, and lowering of the saturation magnetization and anisotropy. The relatively convenient synthesis conditions, along with the tunable magnetic properties, make such materials highly desirable for future magnetic recording technologies. [ABSTRACT FROM AUTHOR]