Spin dependent scattering of a domain-wall of controlled size

Magnetoresistance measurements in the CPP geometry have been performed on single electrodeposited Co nanowires exchange biased on one side by a sputtered amorphous GdCo layer. This geometry allows the stabilization of a single domain wall in the Co wire, the thickness of which can be controlled by an external magnetic field. Comparing magnetization, resistivity, and magnetoresistance studies of single Co nanowires, of GdCo layers, and of the coupled system, gives evidence for an additional contribution to the magnetoresistance when the domain wall is compressed by a magnetic field. This contribution is interpreted as the spin dependent scattering within the domain wall when the wall thickness becomes smaller than the spin diffusion length.Comment: 9 pages, 13 figure

Combined spin valve and anisotropic magnetoresistance in NiFe/Cu/NiFe layered thin films

We present a theoretical study of the combined effect of spin valve and anisotropic magnetoresistance in NiFe/Cu/NiFe layered thin films, using an extended form of the semiclassical Camley and Barnas model for electron transport. The anisotropic magnetoresistance is treated by introducing spin-dependent anisotropic mean free paths in the NiFe layers. From calculations of both magnetoresistance effects as a function of NiFe and Cu thickness, we discuss the validity of a description of the combined effect in terms of a simple summation of spin valve and anisotropic magnetoresistance.</p

Combined spin valve and anisotropic magnetoresistance in NiFe/Cu/NiFe layered thin films

We present a theoretical study of the combined effect of spin valve and anisotropic magnetoresistance in NiFe/Cu/NiFe layered thin films, using an extended form of the semiclassical Camley and Barnas model for electron transport. The anisotropic magnetoresistance is treated by introducing spin-dependent anisotropic mean free paths in the NiFe layers. From calculations of both magnetoresistance effects as a function of NiFe and Cu thickness, we discuss the validity of a description of the combined effect in terms of a simple summation of spin valve and anisotropic magnetoresistance

Effects of interface intermixing on the magnetoresistance of spin valves with uncoupled Co-layers

We have studied the effect of an artificially intermixed region grown at the interfaces of Co/Cu spin valves with uncoupled layers. Two different structures are used: exchange-biased spin valves and engineered spin valves in which two layers are antiferromagnetically coupled and a third layer, on top of this system, is not coupled to the other two. It is shown that structural effects, induced by variation of the deposition parameters and by the intermixing can play an important role. Since the present study uses sputtered layers an intrinsic initial intermixing of 4-5 angstrom is already present. For both types of spin valves Gp, ΔG and ΔR/R all show a gradual decrease when the nominal thickness of the total intermixed region is enlarged from 0 to 36 angstrom. Also when the initial degree of intermixing is decreased by sputtering at higher Ar-pressure, Gp, ΔG and ΔR/R still show a gradual decrease as a function of intermixed layer thickness. Combined with the fact that there is no difference between an intermixed region of thickness t at one Co/Cu interface or intermixed regions of thickness t/2 at two interfaces, this indicates that the electron scattering in the intermixed region is predominantly spin independent, although this region preserves a magnetic moment.</p

Interplay between exchange biasing and interlayer exchange coupling in Ni80Fe20/Cu/Ni80Fe20/Fe 50Mn50 layered systems

Magnetoresistance curves have been measured for 80 Å Ni 80Fe20/tCu Cu/60 Å Ni80Fe 20/80 Å Fe50Mn50 layered systems (t Cu=9-93 Å). After separating the contributions from anisotropic magnetoresistance and spin valve or giant magnetoresistance (GMR), the GMR curves were interpreted in terms of a minimum-energy model for the magnetization orientation of the Ni80Fe20 layers. The interlayer exchange coupling was found to be purely ferromagnetic, and monotonically decreasing with increasing tCu. The interplay of this coupling with the exchange biasing effect results in a critical interlayer thickness, t critCu=15 Å, below which no perfect antiparallel alignment of the Ni80Fe20 magnetizations can be realized. The GMR, which would otherwise increase with decreasing Cu layer thickness, is therefore expected to reach a maximum at or slightly below tcrit Cu. Indeed, such a maximum was found (with ΔR/R=4.3%) at t Cu=22 Å, a value well above tcritCu. This is attributed to the occurence of inhomogeneities in the interlayer exchange coupling

Magnetoresistance in Ni80Fe20/Cu/Ni 80Fe20/Fe50Mn50 spin valves with low coercivity and ultrahigh sensitivity

We present magnetoresistance measurements on Ni80Fe 20/Cu/Ni80Fe20/Fe50Mn50 spin valves with crossed anisotropies: the easy magnetization direction of the unbiased Ni80Fe20 layer is perpendicular to the exchange biasing field which effectively works on the second Ni80Fe 20 layer due to the interaction with the Fe50Mn 50 layer. The hysteresis in the low-field magnetoresistance is less than 0.03 kA/m, which is ten times smaller than the hysteresis for similar materials with parallel anisotropies. The sensitivity (∂R/R ∞)/∂H ranges from 8% to 18%/(kA/m), depending on the preparational method. To our knowledge this combination of very high sensitivity and very low coercivity has not been reported before

Effects of interface intermixing on the magnetoresistance of spin valves with uncoupled Co-layers

We have studied the effect of an artificially intermixed region grown at the interfaces of Co/Cu spin valves with uncoupled layers. Two different structures are used: exchange-biased spin valves and engineered spin valves in which two layers are antiferromagnetically coupled and a third layer, on top of this system, is not coupled to the other two. It is shown that structural effects, induced by variation of the deposition parameters and by the intermixing can play an important role. Since the present study uses sputtered layers an intrinsic initial intermixing of 4-5 angstrom is already present. For both types of spin valves Gp, ΔG and ΔR/R all show a gradual decrease when the nominal thickness of the total intermixed region is enlarged from 0 to 36 angstrom. Also when the initial degree of intermixing is decreased by sputtering at higher Ar-pressure, Gp, ΔG and ΔR/R still show a gradual decrease as a function of intermixed layer thickness. Combined with the fact that there is no difference between an intermixed region of thickness t at one Co/Cu interface or intermixed regions of thickness t/2 at two interfaces, this indicates that the electron scattering in the intermixed region is predominantly spin independent, although this region preserves a magnetic moment

High-Q integrated RF passives and micro-mechanical capacitors on silicon

The PASSI™ technology platform is described for the integration of low-loss inductors, capacitors, and MEMS on high-ohmic Si substrates. Using this platform the board space area taken up by e.g. impedance matching circuits can be reduced by 50%. The losses of passives induced by the semi-conducting Si substrate can effectively be suppressed using a combination of surface amorphisation and e-beam irradiation. The incorporation of MEM tuneable capacitors in high-Q inductor-capacitor networks is demonstrated