Co-based Alloy Thin Films Research Articles

Hall current sensor IC with integrated Co-based alloy thin film magnetic concentrator

This work deals with a cobalt-based alloy thin film magnetic concentrator (MC) which is fully integrated on a Hall sensor integrated circuit (IC) developed in the 0.35 µm Bipolar CMOS DMOS (BCD) technology on 8” silicon wafer. An amorphous magnetic film with a thickness of 1µm, coercitive field Hc MS ) of 0.45T has been obtained with a sputtering process. The Hall sensor IC has shown sensitivity to magnetic field at room temperature of 240V/AT without concentrator and 2550V/AT with concentrator, gaining a factor of 10.5. A current sensor demonstrator has been realized showing linear response in the range -50 to 50A.

Magnetic interactions in Co-based alloy thin films

The interactions in ternary and quaternary Co-based alloy thin films for longitudinal recording media, with different thickness, are studied. The analysis is performed through the measurement of the initial magnetization and ordinary hysteresis curves. The interactions result stronger in quaternary than in ternary alloy films and when the film thickness is smaller. These findings are discussed in relationship with the evolution of the magnetization switching, characterized by a tendency towards a more coherent rotation of the magnetization in single-domain grains of thinnest and quaternary films, owing to the complex structure of these films. The impact of this evolution on the thermal stability of the magnetic properties is also discussed.

Thermal stability of magnetic properties in ternary and quaternary Co-based alloy thin-film media

Co-based alloy thin films for longitudinal recording media are analysed. The magnetic stability of such media is studied with measurements of magnetization decay and of coercivity variation with the applied field sweep rate. The analysed films have different composition (ternary and quaternary Co alloy) and different thickness. Consequently they show different stabilities. Besides, the magnetization switching of the various films is diversified, as indicated by the rotational hysteresis analysis. The impact of such evolution on the thermal stability of the magnetic properties of the thin-film media is underlined.

Structural, magnetic and magnetotransport properties of thin films of the Heusler alloys Cu 2MnAl, Co 2MnSi, Co 2MnGe and Co 2MnSn

We report structural, magnetic and transport properties of thin films of the Heusler compounds Cu 2MnAl, Co 2MnSi, Co 2MnGe and Co 2MnSn prepared by RF-sputtering. Cu 2MnAl grows epitaxially on MgO (1 0 0), for the Co-based Heusler compounds it is possible to induce (1 1 0)-growth on Al 2O 3 a-plane by the use of metallic seed layers. The Co-based alloy thin films grow in the ordered L2 1 structure and essentially preserve the full ferromagnetic magnetization of the bulk. The electrical conductivity is rather low indicating substantial magnetic or structural disorder.

Enhanced coercivity by substrate bias configuration in Co-based alloy thin film

Using the substrate bias configuration in a single sputtering process, Co-based alloy triple-layer magnetic thin films were deposited. A coercivity increase was obtained in both room-temperature-deposited and high-temperature-deposited (300 °C) films, and the coercivity was optimized in a NB–B–NB (NB: no bias and B: bias applied in sputtering) type of bias configuration. Dislocation and voids introduced by bias sputtering and the diffusion at the grain boundary and interfaces were proposed to explain the improvement of coercivity. The bias-configured sputtering triple-magnetic-layer structure was suggested as a new approach to improve the magnetic properties, which maintain the advantage of multi-magnetic-layer media.

Microstructures and basic magnetic properties of Co-based epitaxial magneticthin films

To investigate the basic magnetic and recording characteristics of Co and Co-based alloy thin films, single crystalline and bicrystalline magnetic thin films are prepared by employing an epitaxial thin film growth technique using MgO(110) and (100) single crystal substrates. Uniaxial magneto-crystalline constants ( K u) and Gilbert's damping constants ( α) of Co, CoCrTa, and CoCrPt thin films are determined by Torque and FMR measurements. (11̄00) oriented single crystalline and (112̄0) oriented bicrystalline Co-based thin films are prepared. K u values of Co, CoCr 16Ta 4, CoCr 15Pt 12 thin films are determined to be 4.5×10 6, 1.7×10 6, 3.3×10 6 erg/cc, respectively. The effect of lattice mismatch between the magnetic layer and the Cr alloy underlayer on K u value of CoCr 15Pt 12 is systematically investigated. The α value of the Co and the Co alloy thin films are determined to be ranging between 0.01–0.04. Recording resolution and noise characteristics of the bicrystalline CoCr 15Pt 20 disk medium are also examined as a function of angle from the effective easy axis of the disk medium.

Co-Based Alloy Thin-Film Media on Carbon Substrates

The mechanical and magnetic properties of thin-film media using newly developed carbon substrates, which offer such advantages as light weight, high heat resistance and nonmagnetic properties, were investigated and compared with the properties of thin-film media prepared using conventional NiP/Al substrates. The adhesive strength of a thin-film medium sputtered onto a carbon substrate is higher than that of film sputtered onto a NiP/Al substrate, because of the formation of Cr-C compounds at the interface between the carbon substrate and the Cr underlayer. The coercivity of a thin-film medium sputtered onto a carbon substrate is also higher than that of film on NiP/Al substrate, because of the unique surface morphology. High coercivity can be obtained by using a circumferentially textured substrate and a bias sputtering method.

Crystal Structure and Magnetic Properties of Co-Based Alloy Thin Film Prepared on Cr Underlayer With Good Crystallite Orientation

ABSTRACTCo85Cr15-xTax(x:0, 2at%)/Cr films with microscopically flat surface were investigated for high density recording media. These films were deposited on silicon wafer and glass substrates at the substrate temperature Ts of 350 °C at argon pressure as low as sub-mTorr by using Facing Targets Sputtering (FTS) apparatus. The elevating of Ts promoted the Cr(200) orientation in film plane, leading to the in-plane c-axis orientation of Co crystallites. Addition of some elements such as Si, Ge and Ta in Cr thin film was found to stabilize Cr(110) crystal orientation even at Ts of 300 °C.