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.

Co(x)Ni(1-x) alloy nanowires with varying Co content (0 ≤ x ≤ 0.95), having a diameter of 130 nm and length of around 20 μm, are synthesized by template-assisted electrodeposition into the nanopores of SiO(2) conformal coated hard-anodic aluminum oxide membranes. The magneto-structural properties of both single isolated nanowires and hexagonally ordered nanowire arrays of Co-Ni alloys are systematically studied by means of magneto-optical Kerr effect magnetometry and vibrating sample magnetometry, respectively, allowing us to compare different alloy compositions and to distinguish between the magnetostatic and magnetocrystalline contributions to the effective magnetic anisotropy for each system. The excellent tunable soft magnetic properties and magnetic bistability exhibited by low Co content Co-Ni nanowires indicate that they might become the material of choice for the development of nanostructured magnetic systems and devices as an alternative to Fe-Ni alloy based systems, being chemically more robust. Furthermore, Co contents higher than 51 at.% allow us to modify the magnetic behavior of Co-rich nanowires by developing well controlled magnetocrystalline anisotropy, which is desirable for data storage applications.

High-quality densely packed hexagonal arrays of Ni nanowires have been prepared by filling self-ordered nanopores in alumina membranes. Nanowires with different diameter d (18–83 nm) and lattice parameter D (65 and 105 nm) have been studied by atomic force, high resolution scanning electron microscopies, Rutherford backscattering, and vibrating sample magnetometer techniques. Axial loops coercivity and remanence decrease with increasing ratio diameter to lattice parameter, r, until nanowires start to interconnect locally. Additionally, hysteresis of in-plane loops increases with packing factor. In order to interpret the experimental results, multipolar magnetostatic interactions among nanowires with increasing ratio r are considered.

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).