[en] A novel micro-fabrication technique has been used to create an array of lateral magnetic multilayers consisting of micron-sized sputtered Co and Ni₈₀Fe₂₀ wires. The structures were fabricated using conventional optical lithography and a combination of hard and soft lift-off methods. For the field applied parallel to the wires intrinsic easy axis, we observed two switching fields corresponding to the distinct coercive field of the Ni₈₀Fe₂₀ wires (H_c1) and Co wires (H_c2) constituting the lateral multilayer wire array. A state of anti-parallel relative alignment of magnetization was observed when the applied field is greater than the switching field of Ni₈₀Fe₂₀ wires but less than the switching field of Co wires. We found the region of anti-parallel alignment of magnetization between the Co and Ni₈₀Fe₂₀ wires to be very sensitive to the relative orientation of the applied magnetic field

[en] The magnetostatic coupling in lithographically defined 25 nm thick Ni₈₀Fe₂₀ wire arrays has been investigated using magnetoresistance (MR) measurements. The structures consist of array of micron-size wires with inter-wire spacings in the range from 50 nm to 2 μm. For the field applied along the easy axis of the magnetostatically coupled wire array, a novel magnetoresistance behaviour is observed which we explain in terms of anti-parallel alignment of magnetisation in adjacent wires in the array. The MR response to the field applied along the hard axis is found to be very sensitive to the inter-wire spacing due to magnetostatic interactions. Our observations show that magnetostatic coupling is an important parameter in the design of magnetic devices

[en] Effects of in situ magnetic field deposition and post-deposition magnetic annealing on the exchange field and coercivity of Fe₅₀Mn₅₀(200 A)/Ni₈₀Fe₂₀ bilayers over a range of 40-120 A Ni₈₀Fe₂₀ thicknesses were investigated. A large increase in coercivity and exchange field was observed in samples that were annealed at 230 deg. C for 15 min in vacuum. The structure with 80 A Ni₈₀Fe₂₀ thickness was found to exhibit maximum exchange field in the range of thickness investigated. The non-monotonic dependence of exchange bias with ferromagnetic layer thickness suggests the important role played by the microstructure of the Fe₅₀Mn₅₀ antiferromagnetic AF layer. These phenomena are discussed in relation to surface roughness, grain sizes, diffusion and magnetic domains

[en] We have investigated the magnetic properties of rectangular antidot (2x10 μm²) arrays embedded into 80 nm thick continuous permalloy films with the inter-hole spacing of 2 and 6 μm. We observed that the presence of the rectangular hole structures strongly modifies the shape of M-H loops, when compared with the reference continuous film. Specifically, the coercivity increases drastically as the inter-hole spacing is reduced. This is in agreement with our magnetic force microscopy images. Marked changes in both the shape and sign of the magnetoresistance curve were also observed

[en] We have investigated the exchange bias effect in micron-sized ferromagnetic wires made from Co and Ni₈₀Fe₂₀ films. The wires were fabricated using optical lithography, metallization by sputtering and lift-off technique. Magnetotransport measurements were performed at temperatures ranging from 3 to 300 K. We observed marked changes in the magnetoresistance (MR) properties as the temperature is varied. At 300 K, the field at which the sharp peak occurs corresponding to the magnetization reversal of the Co wires is 167 Oe and is symmetrical about the origin. As the temperature was decreased to 3 K, we observed a shift in the peak positions of the MR characteristics for both the forward and reverse field sweeps corresponding to a loop shift of 582 Oe in the field axis. The asymmetric shift in the MR loops at low temperatures clearly indicates the exchange bias between ferromagnetic (Co) and antiferromagnetic parts (Co-oxide at the surfaces) from natural oxidation. Ni₈₀Fe₂₀ wires of the same geometry showed similar effect with a low exchange bias field. The onset of exchange biasing effect is found to be 70 and 15 K for the Co and Ni₈₀Fe₂₀ wires, respectively. A striking effect is the existence of exchange biasing effect from the sidewalls of the wires even when the wires were capped with Au film

[en] The effects of in situ magnetic field deposition and postdeposition magnetic annealing on the exchange field and coercivity of Ni₈₀Fe₂₀/Fe₅₀Mn₅₀/Ni₈₀Fe₂₀ trilayers were investigated. Hysteresis loops reveal a one-sided plateau for unannealed samples, A clean loop without plateau was observed for samples annealed at 230 deg. C for 15 min in vacuum with an external magnetic field. An increase in coercivity was also observed. This can be attributed to the formation of NiFeMn alloy at the interfaces caused by annealing

[en] We have investigated in detail the electronic transport properties of half metallic CrO₂ powder-based devices, fabricated using optical lithography and field alignment technique. A transition in the conduction mechanism from spin-dependent intergranular tunneling to inelastic hopping was observed at 215 K. This transition temperature shifts to 230 K in the presence of 10 kOe field cooling due to reduction of the spin-independent hopping conductance channel. I-V characteristics exhibit strong temperature dependence and are non-linear even at room temperature. Our experimental results are in good agreement with a simple theoretical model. A novel 'double switching' phenomenon was observed in the I-V curves below the transition temperature

[en] We have successfully demonstrated the detection of pseudo-magnetic beads placed on top of 4x4 μm² and 5x5 μm² Planar Hall trilayer (Si/Co_10nm /Cu_2nm /NiFe_10nm) sensors. The sensor and the pseudo-magnetic beads were fabricated using a combination of e-beam and optical lithography techniques. Magneto-transport measurements detect the presence of dots placed on top of the PHE junction, even to the limit of single-dot. We observed that the PHE response is very sensitive to changes in the density of coverage of the sensing area with pseudo-magnetic beads. We attribute this effect to the direct coupling between the dots and the sensing layer below

[en] We have investigated the evolution of magnetic spin states and in-plane magnetic anisotropy in arrays of elongated Ni₈₀Fe₂₀ rings. Large area (4x4 mm²) elongated Ni₈₀Fe₂₀ nanorings of thickness in the range from 5 to 60 nm were fabricated using deep ultraviolet lithography at 248 nm exposing wavelength. The magnetic spin states and the magnetization reversal processes are strongly dependent on the ring thickness and in-plane magnetic anisotropy due to the elongation of the rings. Our experimental results are in a very good agreement with micromagnetic simulations

[en] Anisotropy of linear and nonlinear magnetooptical (MO) effects in a regular array of Py antidots is studied by means of the MO Kerr effect at the fundamental and second harmonic wavelengths. We have demonstrated that the value of the MO effect, coercivity, and magnetization distribution depend substantially on the azimuthal orientation of the antidots array relatively to the external magnetic field. - Highlights: • The results from the anisotropy of Py antidots are presented. • The hard magnetization axis is oriented along the side of the antidot square lattice. • The value of the saturated LMOKE effect is isotropic. • The maximum of the SHG magnetic contrast was observed along easy axis.