http://files.janapv.webnode.cz/200000097-8a03f8afdf/ex_bias_nano.pdf

Exchange bias in nanostructures

Magnetocaloric effect: From materials research to refrigeration devices

Magnetic Heusler alloys which undergo a martensitic transition display interesting functional properties. In the present review, we survey the magnetocaloric effects of Ni-Mn-based Heusler alloys and discuss their relation with the magnetic shape-memory and magnetic superelasticity reported in these materials. We show that all these effects are a consequence of a strong coupling between structure and magnetism which enables a magnetic field to rearrange martensitic variants as well as to provide the possibility to induce the martensitic transition. These two features are respectively controlled by the magnetic anisotropy of the martensitic phase and by the difference in magnetic moments between the structural phases. The relevance of each of these contributions to the magnetocaloric properties is analysed.

https://iopscience.iop.org/article/10.1088/0953-8984/21/23/233201/pdf

Magnetocaloric effect and its relation to shape-memory properties in ferromagnetic Heusler alloys

We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

Theory of the linear and nonlinear optical properties of semiconductor microcrystallites

In order to study the effects of iron oxide (IO) nanoparticles on Staphylococcus aureus, IO nanoparticles were synthesized via a novel matrix-mediated method using polyvinyl alcohol (PVA). The IO nanoparticles were characterized by transmission electron microscopy and dynamic light scattering. Further, S. aureus were grown in the presence of three different IO nanoparticle concentrations for four, 12, and 24 hours. Live/dead assays were performed and the results provide evidence that IO/PVA nanoparticles inhibited S. aureus growth at the highest concentration (3 mg/mL) at all time points.

/pdf/bactericidal-effect-of-iron-oxide-nanoparticles-on-gnrk4o0y6u.pdf

Bactericidal effect of iron oxide nanoparticles on Staphylococcus aureus

ac susceptibility, sound velocity, and internal friction study of the martensitic transformation in melt-quenched (site-disordered) Ni55Fe20Al25 alloy unravels the irreversible thermoelastic changes (thermal hysteresis) that occur in the austenite phase in the premartensitic regime. In the heating cycle, the system retains the “memory” of the initiation and subsequent growth of the martensitic phase (at the expense of the parent austenite phase) that had taken place during the cooling cycle in the austenite-martensite phase coexistence region. These and other findings are discussed in this communication.

/pdf/dynamic-elastic-properties-and-magnetic-susceptibility-3dnucqde5k.pdf

Dynamic elastic properties and magnetic susceptibility across the austenite-martensite transformation in site-disordered ferromagnetic Ni-Fe-Al alloy

Temperature dependent synchrotron x-ray powder diffraction, differential scanning calorimetry, and magnetic measurements were performed on Ni2+xMn1-xGa (x=0.20 and 0.35) magnetic shape memory alloys. For x=0.20, though the monoclinic phase is thermodynamically stable, a trace of residual stress can stabilize a tetragonal phase.
The residual-stress-induced tetragonal phase transforms to the cubic austenite phase over an unusually large temperature range (348 K < T < 693 K), suggesting extremely slow kinetics of transformation. In contrast to x=0.20, the thermodynamically stable phase of x=0.35 is
tetragonal and this composition exhibits the usual features of a reversible martensitic transformation. The results suggest that for x=0.20 the monoclinic and tetragonal phases are nearly degenerate.

Competing tetragonal and monoclinic phases in Ni2.2Mn0.80Ga

Magnetorheology in CoNi nanoplatelet-based MRFs: Effect of platelet orientation and oscillatory shear

Magnetic field induced synthesis and self-assembly of super paramagnetic particles in a protein matrix.

The authors report the design and construction of a very simple vibrating reed apparatus with automatic frequency locking capability where the resonance frequency and the internal friction can be recorded continuously as a function of temperature. The apparatus is particularly suitable for studies down to liquid helium temperatures or below.

P. K. Mukhopadhyay

Papers

Dynamic elastic properties and magnetic susceptibility across the austenite-martensite transformation in site-disordered ferromagnetic Ni-Fe-Al alloy

Competing tetragonal and monoclinic phases in Ni2.2Mn0.80Ga

Magnetorheology in CoNi nanoplatelet-based MRFs: Effect of platelet orientation and oscillatory shear

Magnetic field induced synthesis and self-assembly of super paramagnetic particles in a protein matrix.

A simple vibrating reed apparatus for use at low temperatures