Soft magnetic $ rm Ni sb{ it x}Co sb{ it 100-x}$/Cu multilayers in the range x = 20 to 80 have been prepared by DC-magnetron sputtering. NiCo alloys were chosen because of their small magnetoelastic parameters around the range x = 70-80 and very small lattice mismatch between NiCo and Cu. This combination of parameters should lead to good giant magnetoresistance (GMR) with a small saturation field. Structural characterization reveals that high quality layered structures were obtained. Quantitative interpretation of the superlattice structure parameters, such as interface roughness, interfacial mixing profiles and layer-thickness disorders, have been carried out by modelling the X-ray diffraction data. / GMR was found to be largest at x = 80 with well-defined oscillations as a function of the thickness of the Cu layer, mirroring the interlayer magnetic coupling. In particular, GMR with small saturation fields around Cu thickness near the second MR maximum (t$ sb{Cu}$ = 20A) will be technologically important because of the very high magnetic field sensitivity. Correlating the multilayer structure to the GMR allow us to optimize the structural parameters by enhancing the spin-dependent interfacial scattering in a high quality layered structure. Direct observation of the simple antiferromagnetic order has been achieved by the presence of the (0,0,${1 over2})$ wavevector in small angle neutron scattering experiments. A near-perfect antiferromagnetic spin arrangement is found for a Cu thickness t$ sb{Cu}$ = 20 A, that can be readily aligned ferromagnetically in a small external field of less than 200 Oe. / A complementary system, FM/Ag (FM = $ rm Ni sb{81}Fe sb{19}, Ni sb{80}Co sb{20}$ and $ rm Ni sb{66}Co sb{18}Fe sb{16})$ granular multilayer prepared by annealing multilayers, has also been studied. Enhanced magnetoresistance observed in these systems is shown to be controlled by the size, concentration and thermal stability of the magnetic precipitates in a nonmagnetic matrix. For a particular multilayer structure with a magnetic layer of 20 A, annealed at around 325$ sp circ$C, a GMR of $ sim$4% with a characteristic saturation field of 10 Oe was found, leading to a high magnetoresistive sensitivity of $ sim$0.4%/Oe at room temperature.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28680 |
| Date | January 1994 |
| Creators | Bian, Xiaoping |
| Contributors | Strom-Olsen, John O. (advisor), Altounian, Zaven (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001448885, proquestno: NN05672, Theses scanned by UMI/ProQuest. |
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