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Biomedical subjects

B Jankó

Publications and source records attributed to B Jankó.

9 recordsLinked to original sources
PubMed2006

Dynamics, rectification, and fractionation for colloids on flashing substrates.

We show that a rich variety of dynamic phases can be realized for mono- and bidisperse mixtures of interacting colloids under the influence of a symmetric flashing periodic substrate. With the addition of dc or ac drives, phase locking, jamming, and new types of ratchet effects occur. In some regimes we find that the addition of a nonratcheting species increases the velocity of the ratcheting particles. We show that these effects occur due to the collective interactions of the colloids.

Journal Article↗
PubMed2005

Magnetic scattering of spin polarized carriers in (In, Mn)Sb dilute magnetic semiconductor.

Magnetoresistance measurements on the magnetic semiconductor (In, Mn)Sb suggest that magnetic scattering in this material is dominated by isolated Mn2+ ions located outside the ferromagnetically ordered regions when the system is below T(c). A model is proposed, based on the p-d exchange between spin-polarized charge carriers and localized Mn2+ ions, which accounts for the observed behavior both below and above the ferromagnetic phase transition. The suggested picture is further verified by high-pressure experiments, in which the degree of magnetic interaction can be varied in a controlled way.

Journal Article↗
PubMed2005

Pressure-induced ferromagnetism in (In,Mn)Sb dilute magnetic semiconductor.

Recent advances in III(1-x)Mn(x)V ferromagnetic semiconductors (for example in Ga(1-x)Mn(x)As) have demonstrated that electrical control of their spin properties can be used for manipulation and detection of magnetic signals. The Mn(2+) ions in these alloys provide magnetic moments, and at the same time act as a source of valence-band holes that mediate the Mn(2+)-Mn(2+) interactions. This coupling results in the ferromagnetic phase. In earlier workit was shown that the ferromagnetic state can be enhanced or suppressed by varying the carrier density. Here we demonstrate that, by using hydrostatic pressure to continuously tune the wavefunction overlap, one can control the strength of ferromagnetic coupling without any change in the carrier concentration. Tuning the exchange coupling by this process increases the magnetization spectacularly, and can even induce the ferromagnetic phase in an initially paramagnetic alloy. These results may open new directions for strain-engineering of nanodevices.

Alloys↗
PubMed2003

Structure and melting of two-species charged clusters in a parabolic trap.

We consider a system of charged particles interacting with an unscreened Coulomb repulsion in a two-dimensional parabolic confining trap. The static charge on a portion of the particles is twice as large as the charge on the remaining particles. The particles separate into a shell structure with those of greater charge situated farther from the center of the trap. As we vary the ratio of the number of particles of the two species, we find that for certain configurations, the symmetry of the arrangement of the inner cluster of singly charged particles matches the symmetry of the outer ring of doubly charged particles. These matching configurations have a higher melting temperature and a higher thermal threshold for intershell rotation between the species than the nonmatching configurations.

Journal Article↗
PubMed2001

Collective interaction-driven ratchet for transporting flux quanta.

We propose and study a novel way to produce a dc transport of vortices when applying an ac electrical current to a sample. Specifically, we study superconductors with a graduated random pinning density, which transports interacting vortices as a ratchet system. We show that a ratchet effect appears as a consequence of the long range interactions between the vortices. The pinned vortices create an asymmetric periodic flux density profile, which results in an asymmetric effective potential for the unpinned interstitial vortices. The latter exhibit a net longitudinal rectification under an applied transverse ac electric current.

Journal Article↗