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This work reports the pore‐filling of porous silicon (PSi) and the loading of silicon nanotubes (SiNTs) with Pt‐Fe nanoparticles (NPs) and the corresponding different magnetic behavior of the two composite systems. The fabrication of magnetic hard/soft nanostructures is in demand for the purpose of achieving both a high energy product as well as the replacement of rare earth permanent magnets. Pt‐Fe templated by PSi shows a higher coercivity and remanence than SiNTs/Pt‐Fe and thus a higher hard magnetic performance, the difference between coercivities being about 57%. Considering that the Pt‐Fe deposits employ different molar ratios of Pt to Fe the coercivities vary in a range of 5% in the case of both template types. Comparing Pt‐Fe loaded samples with Co‐loaded samples in all cases, an increase of the coercivity and the remanence is observed for Pt‐Fe, whereas in the case of PSi as template material the increase is significantly stronger (about twice as much) than in the case of SiNTs samples. Furthermore, the samples are investigated at high temperatures up to 950 K to determine the Curie temperature of the systems. [ABSTRACT FROM AUTHOR]

Herein, nanostructured silicon is fabricated with two different embedded magnetic nanostructures (Ni/Co) to exploit the magnetic properties of both metals and discern the behavior of the exchange coupling between the two—especially with respect to their volume ratio. A variation of the size as well as the volume ratio of the two metals modifies the exchange coupling and thus the energy product. Two templates are utilized: one involves the use of porous silicon (PSi) and the other entails porous silicon nanotubes (SiNTs). In the case of Psi, the bimetallic structures (Ni/Co) are electrodeposited, whereas in the case of SiNTs, Co is chemically grown within the tubes followed by the deposition of Ni on the outside. The magnetic properties of the systems strongly depend on the geometry of the deposits, on the volume ratio of the two metals, as well as on the proximity of the deposits. If the distance is small enough magnetic exchange coupling is present. Due to their size and the coupling of the bimetallic structures, the switching behavior of the hysteresis can be varied. Ultimately, nanocomposites with an energy product as high as possible is achieved to give rise to applications as permanent nanomagnets. [ABSTRACT FROM AUTHOR]

This paper represents a short overview of nanocomposites consisting of magnetic nanoparticles incorporated into the pores of a porous silicon matrix by two different methods. On the one hand, nickel is electrochemically deposited whereas the nanoparticles are precipitated on the pore walls. The size of these particles is between 2 and 6 nm. These particles cover the pore walls and form a tube-like arrangement. On the other hand, rather well monodispersed iron oxide nanoparticles, of 5 and 8 nm respectively, are infiltrated into the pores. From their size the particles would be superparamagnetic if isolated but due to magnetic interactions between them, ordering of magnetic moments occurs below a blocking temperature and thus the composite system displays a ferromagnetic behavior. This transition temperature of the nanocomposite can be varied by changing the filling factor of the particles within the pores. Thus samples with magnetic properties which are variable in a broad range can be achieved, which renders this composite system interesting not only for basic research but also for applications, especially because of the silicon base material which makes it possible for today's process technology. [ABSTRACT FROM AUTHOR]

In this paper, the magnetic interactions between metal nanostructures deposited within the pores of porous silicon will be elucidated. The influence of the morphology of the porous silicon which means a variation between high, medium, and low dendritic pore-growth as well as the morphology of the metal deposits (geometry, distribution and correlated branches to the template, respectively) on the magnetic behavior will be figured out. An increase in the uniformity of the pores resulting in smoother metal deposits leads to an increase in the coercivity of the nanocomposite which reveals less cross-talk between the nanostructures due to a modification of the stray fields. Also superparamagnetic nanoparticles of different sizes are incorporated within the pores and the dipolar coupling between them with regard to their sizes and their arrangements are investigated. [ABSTRACT FROM AUTHOR]