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.

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.

We determined the magnetic entropy change and refrigerant capacity of melt spun ${\mathrm{Ni}}_{50.3}{\mathrm{Mn}}_{35.5}{\mathrm{Sn}}_{14.4}$ ribbons around both the structural and the magnetic transitions for a field of $20\mathrm{kOe}$ . The maximum entropy changes at the structural and magnetic transitions were of 4.1 and $-1.1\mathrm{J}{\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$ . Ribbons studied show a larger refrigerant capacity around the magnetic transition $\left(46\mathrm{J}{\mathrm{kg}}^{-1}\right)$ than around the structural transition $\left(26\mathrm{J}{\mathrm{kg}}^{-1}\right)$ , suggesting that the temperature range at the magnetic transition is more adequate for a refrigerant cycle than that at the structural transition.

Inverse and direct magnetocaloric properties were evaluated in preferentially textured ${\text{Mn}}_{50}{\text{Ni}}_{40}{\text{In}}_{10}$ ribbons applying the magnetic field $H_{\parallel }$ along the ribbon length and perpendicular $H_{\perp }$ to the ribbon plane $\left(\Delta H=30\text{kOe}\right)$ . Maximum magnetic entropy change, hysteretic losses, and refrigerant capacity were not significantly affected by crystallographic texture. Refrigeration capacity around structural transition is strongly reduced by the large hysteretic losses associated to the metamagnetic field-induced reverse martensitic transformation and narrower working temperature range making the interval around the magnetic transition more efficient for a refrigerant cycle ($R{C}^{\text{struct}}=71\text{J}{\text{kg}}^{-1}$ versus $RC^{\text{struct}}{}_{\text{eff}}\approx 60\text{J}{\text{kg}}^{-1}$ , and $R{C}^{\text{magn}}=89–86\text{J}{\text{kg}}^{-1}$ , for $H_{\parallel }$ and $H_{\perp }$ , respectively).

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 $150\mathrm{K}$ .