Gigahertz magnetoimpedance (MI) curves obtained in an exchange biased Ni81Fe19/Fe50Mn50 multilayer are reported. Experimental MI curves are shifted by the exchange bias field (HEB), following the features presented by the hysteresis curves. Theoretical MI curves, calculated using the classical expression for the impedance of a planar magnetic conductor, describe well the experimental data. The results open possibilities for application of exchanged biased MI multilayered materials for the development of autobiased linear magnetic field sensors.

The effect of high energy ball milling on the structural, magnetic and magnetocaloric properties of Ni50Mn36Sn14 Heusler-type alloy has been studied. X-ray diffraction results have revealed a reduction in the crystalline grain size concomitantly with defect inclusions in the crystalline lattice, favouring a chemical disorder effect that transforms the L21–B2-type disordered structure to a simple cubic B2-type structure for increasing milling time. From magnetometry and Mössbauer spectroscopy results, a decrease in the ferromagnetic exchange interaction contribution, an enhancement of the effective exchange bias field and a significant reduction in the magnetic entropy change of the milled alloy are observed.

No abstract

Magnetic properties of sputtered NiFe/IrMn/Co trilayers grown on different seed layers (Cu or Ta) deposited on Si (100) substrates were investigated by magnetometry and ferromagnetic resonance measurements. Exchange bias effect and magnetic spring behavior have been studied by changing the IrMn thickness. As shown by X-ray diffraction, Ta and Cu seed layers provoke different degrees of (111) fcc-texture that directly affect the exchange bias and indirectly modify the exchange spring coupling behavior. Increasing the IrMn thickness, it was observed that the coupling angle between the Co and NiFe ferromagnetic layers increases for the Cu seed system, but it reduces for the Ta case. The results were explained considering (i) different anisotropies of the Co and IrMn layers induced by the different degree of the (111) texture and (ii) the distinct exchange bias set at the NiFe/IrMn and IrMn/Co interfaces in both systems. The NiFe and Co interlayer coupling angle is strongly correlated with both exchange bias and exchange magnetic spring phenomena. It was also shown that the highest exchange bias field occurs when an unstressed L12 IrMn structure is stabilized.

Magnetic properties of sputtered Gd thin films grown on Si (100) substrates kept at two different temperatures were investigated using X-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements. The obtained Gd thin films have a mixture of hcp and fcc structures, but with their fractions depending on the substrate temperature TS and film thickness x. Gd fcc samples were obtained when TS = 763 K and x = 10 nm, while the hcp structure was stabilized for lower TS (300 K) and thicker film (20 nm). The fcc structure is formed on the Ta buffer layer, while the hcp phase grows on the fcc Gd layer as a consequence of the lattice relaxation process. Spin reorientation phenomenon, commonly found in bulk Gd species, was also observed in the hcp Gd thin film. This phenomenon is assumed to cause the magnetization anomalous increase observed below 50 K in stressed Gd films. Magnetic properties of fcc Gd thin films are: Curie temperature above 300 K, saturation magnetization value of about 175 emu/cm3, and coercive field of about 100 Oe at 300 K; features that allow us to classify Gd thin films, with fcc structure, as a soft ferromagnetic material.

No abstract

No abstract

The ferromagnetic resonance (FMR) technique is used to study the exchange bias field in asymmetrical NiFe∕FeMn∕NiFe trilayers produced by dc magnetron sputtering under different working pressures. The FMR spectra give evidence of two resonance modes attributed to the two asymmetrical noninteracting NiFe layers. The study of the in-plane angular dependence of the absorption field allows the measurement of the exchange bias field at both bottom ferromagnetic (FM)∕antiferromagnetic (AFM) and top AFM∕FM interfaces.