We study the magnetoimpedance effect, using a ${\mathrm{Co}}_{67}{\mathrm{Fe}}_4{\mathrm{Mo}}_{\text{1.5}}{\mathrm{Si}}_{\text{16.5}}{\mathrm{B}}_{11}$ amorphous, ribbon-based sensitive element, in the presence of a commercial Ferrofluid^® liquid thin layer covering the ribbon surface. The magnetoimpedance response is clearly dependent on the presence of the magnetic ferroliquid, the value of the applied magnetic field, and the parameters of the driving current. The magnetoimpedance-based prototype is proposed as a biosensor with high sensitivity to the fringe field produced by magnetic nanoparticles. A special advantage of this sensor is its high stability to chemical aggressive media; hence, it can be used for in situ measurements during fabrication of biomaterials with a high level of affinity and specificity with nanoparticles employed as bimolecular labels.

The giant magneto‐impedance effect (GMI) is studied as a function of the structural modification induced in an Fe73.5Si13.5B9Cu1Nb3amorphous alloy wire by annealing. The values of GMI are correlated to those structural changes and with the corresponding variation of the magnetic properties and intrinsic resistivity. Excellent soft magnetic properties, associated with low resistivity values, make this nanostructured material as one of the most promising for future applications of the GMI effect. The tailoring of the structure which can be induced by adequate thermal treatments easily allows one to obtain excellent combinations of circumferential permeability μφ and resistivity ρ during different devitrification stages, in order to produce materials for specific aims. Maximum GMI ratios of 200% are found after annealing the wires in the range 550–600 °C, where an optimum compromise between μφ and ρ is found. A simple model is developed correlating the fundamental physical properties of the soft magnetic wires with the measured values of both components of the impedance, allowing the prediction of experimental GMI ratios and an easy visualization of the phenomenon.

Heusler alloy ${\mathrm{Mn}}_{50}{\mathrm{Ni}}_{40}{\mathrm{In}}_{10}$ was produced as preferentially textured ribbon flakes by melt spinning, finding the existence of martensitic-austenic transformation with both phases exhibiting ferromagnetic ordering. A microcrystalline three-layered microstructure of ordered columnar grains grown perpendicularly to ribbon plane was formed between two thin layers of smaller grains. The characteristic temperatures of the martensitic transformation were $M_S=213\mathrm{K}$ , $M_f=173\mathrm{K}$ , $A_S=222\mathrm{K}$ , and $A_f=243\mathrm{K}$ . Austenite phase shows a cubic $L{2}_1$ structure ($a=0.6013\left(3\right)\mathrm{nm}$ at $298\mathrm{K}$ and a Curie point of $311\mathrm{K}$ ), transforming into a modulated fourteen-layer modulation monoclinic martensite.

The Heusler alloy ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{37}{\mathrm{Sn}}_{13}$ was successfully produced as ribbon flakes of thickness around $7–10\mu \mathrm{m}$ melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be $M_S=218\mathrm{K}$ , $M_f=207\mathrm{K}$ , $A_S=224\mathrm{K}$ , and $A_f=232\mathrm{K}$ ; the thermal hysteresis of the transformation is $15\mathrm{K}$ . Ferromagnetic $L{2}_1$ bcc austenite phase shows a Curie point of $313\mathrm{K}$ , with cell parameter $a=0.5971\left(5\right)\mathrm{nm}$ at $298\mathrm{K}$ , transforming into a modulated $7M$ orthorhombic martensite with $a=0.6121\left(7\right)\mathrm{nm}$ , $b=0.6058\left(8\right)\mathrm{nm}$ , and $c=0.5660\left(2\right)\mathrm{nm}$ , at $150\mathrm{K}$ .