Volume 91, Issue 6, 15 March 2002
Index of content:
- MAGNETISM AND SUPERCONDUCTIVITY (PACS 74-76)
91(2002); http://dx.doi.org/10.1063/1.1450259View Description Hide Description
and FeCoV/Ti multilayers having prepared by dc magnetron sputtering are investigated by x-ray diffraction, stress, and magnetization measurements. The x-ray diffraction data of the system show the presence of interstitial N atoms in the FeCoV layers due to reactive sputtering of Ti with nitrogen. The interstitial N causes an expansion of the FeCoV lattice in for small However, for the samples with large no lattice expansion is observed. In addition to the lattice expansion caused by the intake of N atoms, a change in the crystalline texture of FeCoV layers is also observed as indicated by the enhancement of the FeCoV(200) peaks. The magnetic hysteresismeasurements on the samples show that the easy direction of magnetization lies in the plane of the layers. They further show that there are easy and hard axes of magnetization within the plane of the FeCoV layers. The stress anisotropy present in the plane of the samples induces a magnetic anisotropy through magnetostrictive effects leading to the formation of the in- plane easy axis. The hysteresis and stress measurements carried out on these samples clearly show the influence of N on the in-plane magnetic anisotropy. The magnetoelastic energy in the case of the system, calculated from the stress data and from the magnetization measurements as a function of is found to agree over a large range of thickness, whereas the curves deviate significantly for small layer thickness. This deviation may be due to the role of the phase. Hysteresismeasurements also show that the remanence is about 95% for all the samples of the system. In contrast, the coercivity increases linearly with increasing in this system. The coercivity of the FeCoV/Ti system is larger and increases more rapidly with as compared with the system. This behavior is attributed to a smaller grain size in the system due to the reactive sputtering of the Ti layers. However, there is no significant influence of N on the saturation magnetization of both systems.
Interlayer segregation of Cu atoms in Ta/NiFe/Cu/NiFe/FeMn/Ta spin-valve multilayers and its influence on magnetic properties91(2002); http://dx.doi.org/10.1063/1.1450033View Description Hide Description
Experimental results show that the exchange coupling field of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for spin-valvemultilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. In order to find out the reason, the composition and chemical states at the surface of Ta(12 nm)/NiFe(7 nm), Ta(12 nm)/NiFe(7 nm)/Cu(4 nm), and Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) were studied using x-ray photoelectron spectroscopy. The results show that no elements from lower layers float out or segregate to the surface in the first and second samples. However, Cu atoms segregate to the surface of Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) multilayers, i.e., Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors which causes the exchange coupling field of Ta/NiFe/Cu/NiFe/FeMn/Ta to be weaker than that of Ta/NiFe/FeMn/Ta.
91(2002); http://dx.doi.org/10.1063/1.1448884View Description Hide Description
The amorphous alloys and were prepared by copper mold casting, melt spinning, and mechanical alloying. Despite their similar x-ray diffraction patterns, samples display different magnetic and thermal behavior correlated with the method of preparation. The fully amorphous melt-spun ribbons exhibit relatively soft magnetic properties with coercivities ≈40 kA/m at room temperature and a Curie temperature Apparently only the mold-cast cylinders of 3 mm diameter show hard magnetic behavior with a coercivity in the range of 258–270 kA/m (depending on composition) and have approximately the same as that of the melt-spun ribbons. An additional magnetic transition at 585 K due to the presence of phase in the case of cast rod has been observed. Heat treatment above crystallization temperature in as-cast and samples destroys the hard magnetic properties. In contrast, mechanically alloyed amorphous samples are soft magnetic with maximum coercivity up to 11 kA/m but show an entirely different which is rather characteristic of an Fe solid solution. The magnetic properties are discussed in terms of different local atomic environment and cluster sizes in amorphous samples prepared by different methods.
91(2002); http://dx.doi.org/10.1063/1.1450037View Description Hide Description
The phase evolution, microstructure, and magnetic properties of 2, 4, 5, 6) melt-spun ribbons were systematically studied as a function of C content. It was found that the addition of C decreases the glass-forming tendency of the as-spun ribbons significantly. A uniform nanoscale exchange coupled microstructure with an average grain size of 20–25 nm can be developed in the directly quenched ribbons with C contents up to 4 at. %. Further increase of C content to leads to, in the optimally quenched ribbons, the presence of an undesirable phase in addition to the 2:14:1 and α-Fe phases, whereas the alloy ribbon containing 6 at. % C consists almost entirely of the soft magnetic and α-Fe phases. Subsequent annealing induces a transformation of the phase to the 2:14:1 phase in the ribbons with and 6, resulting in the formation of a composite 2:14:1/α-Fe structure having relatively large crystallite sizes. Magnetic measurements revealed that, for the optimally processed samples, replacement of up to 4 at. % of B by C significantly increases the coercivity with only slight reduction in remanence an optimum coercivity of 542 kA/m was obtained in the ribbon compared with 430 kA/m for the ribbon. Excessive substitution of C causes a drastic deterioration of both and due to the microstructural coarsening. Moreover, the Curie temperature of the 2:14:1 phase in the samples decreases progressively with increasing C content from for to for
91(2002); http://dx.doi.org/10.1063/1.1454221View Description Hide Description
Magnetic flux density and current density distributions of films in soft magnetic environments are investigated by magneto-optics. Next to the magnets flux penetration is strongly modified. Current density distributions obtained by an inversion of the law of Biot–Savart show overcritical current densities in the current domains next to the magnets.