Magnetic tunnel junctions (MTJs) have been identified as promising candidates for the development of high-performance, ultra-low field magnetometers due to their high sensitivity, low cost, low power consumption, and small size. However, 1/f noise is often quite large at low frequencies and inevitably becomes one of the most difficult issues in developing a magnetic field sensor with ultrahigh sensitivity. Low-frequency 1/f noise can have both electric and magnetic origins, and it is a result of complex non-linear interactions between many degrees of freedom inside a sensor. Therefore, a reduction of the 1/f noise can be expected for the magnetic sensor with very small dimensions. Here, the dependence of the 1/f noise on voltage and strong hard-axis bias field in deep submicrometer-sized MgO-based MTJs is investigated with various junction sizes. The noise spectra were measured by using a home-built low-frequency noise measurement setup with maximum frequency up to 30 kHz. We find that the noise spectral power density is 1/f-like at low frequencies. The experimental results suggest a relative reduction of 1/f noise with respect to the intrinsic thermal noise in small-sized MTJs. The results may open a new approach for reducing the 1/f noise level in MTJ nanosensors.

Complex magnetic ordering in a porous [Co/Pd]5-IrMn multilayered film is modeled for interpreting its magnetization reversal and magnetoresistance mechanisms and explaining its high-resistive and low-resistive states in opposite external fields.

The ribbons Nd2Fe14B/Fe-Co were prepared with the nominal composition Nd16Fe76B8/40% wt. Fe65Co35by the conventional and the developed magnetic field-assisted melt-spinning (MFMS) techniques. Both ribbons are nanocomposites with the smooth single-phase-like magnetization loops. The 0.32 T magnetic field perpendicular to the wheel surface and assisting the melt-spinning process reduces the grain size inside the ribbon, increases the texture of the ribbon, improves the exchange coupling, and, in sequence, increases the energy product(BH)maxof the isotropic powdered samples of MFMS ribbon in ~9% by comparison with that of the ribbon melt-spun conventionally. The grain size reduction effect caused by the assisted magnetic field has also been described quantitatively. The MFMS technique seems to be promising for producing high-performance nanocomposite ribbons.

Nd 10.5 Fe 83.5−x Ga x B 6 (x=1.5, 3 and 4.5) ribbons were prepared by melt-spinning method with various wheel speeds from 5 to 40 m  s −1. Strong crystallographic texture with c-axis of Nd 2 Fe 14 B crystallites along normal of the ribbon surface was observed. The texture degree can be enhanced by decreasing the quenching rate during solidification of the melt and by increasing the concentration of Ga. Preferred orientation of the nanocrystallites with their size of 10–30 nm is obtained not only by controlling the quenching rate of the melt during solidification but also by appropriately annealing the over-quenched ribbons. The texture of microstructure clearly affects magnetic anisotropy of the ribbons. With increasing concentration of Ga, the magnetic anisotropy of the ribbons is considerably increased. The coercivity above 6.5 kOe and maximum energy products larger than 15 MGOe can be achieved on the ribbons with Ga-concentration of 1.5%.

In this study, we consider a technological approach to obtain a high perpendicular magnetic anisotropy of the Co/Pd multilayers deposited on nanoporous TiO2 templates of different types of surface morphology. It is found that the use of templates with homogeneous and smoothed surface relief, formed on silicon wafers, ensures conservation of perpendicular anisotropy of the deposited films inherent in the continuous multilayers. Also, their magnetic hardening with doubling of the coercive field is observed. However, inhomogeneous magnetic ordering is revealed in the porous films due to the occurrence of magnetically soft regions near the pore edges and/or inside the pores. Modeling of the field dependences of magnetization and electrical resistance indicates that coherent rotation is the dominant mechanism of magnetization reversal in the porous system instead of the domain-wall motion typical of the continuous multilayers, while their magnetoresistance is determined by electron-magnon scattering, similarly to the continuous counterpart. The preservation of spin waves in the porous films indicates a high uniformity of the magnetic ordering in the fabricated porous systems due to a sufficiently regular pores array introduced into the films, despite the existence of soft-magnetic regions. The results are promising for the design and fabrication of future spintronic devices.

The nanomaterials based on metal oxides or semiconductor nanoparticles and nanowires appear to demonstrate the unique physical and also functional properties. Those properties, in general, allow constructing a large number of individual nanodevices for promising applications in nanoelectronics, photonics and biomedical technology. Such individual nanodevices represent interesting building blocks for new type of hierarchical mechanical nano-assembling. Mechanical hierarchical nano-assembly of functional nanoscale/meso-macroscale devices into macroscopic devices opens up the new perspectives for the creating of micro-meso and macrodevices and their arrays for many applications. The report describes the physical principle and design of the shape memory based nanogrippers as well as the preliminary results of the manipulation of CNTs, InP, ZnO nanowires and nanoparticles as building blocks for biomedical sensors.

We have studied systematically the effect of field cooling on the magnetic properties of continuous and porous IrMn/[Co/Pd] films. It is found that the coexistence of two ferromagnetic (FM) phases in the porous film, namely, hard-magnetic and soft-magnetic ones, with significantly different magnetic properties relates to the role of pore edges and modifies its magnetic and magnetoresistive properties. It is shown that annealing of the films with their subsequent cooling in an external magnetic field applied for aligning the magnetic moments in the antiferromagnetic (AFM) IrMn layer improves effectively the uniaxial perpendicular anisotropy of the [Co/Pd] layer and induces unidirectional anisotropy in its hard-magnetic regions, blocking simultaneously the soft-magnetic parts by pinning their magnetic moments along the film plane. Magnetoresistance of both continuous and porous films is found to be determined mainly by electron–magnon scattering, whereas the complex morphology of the porous film providing different orientations of exchange coupling at the AFM/FM interface in different film regions modifies significantly the spin-dependent electron transport. The revealed asymmetry of the field dependences of magnetoresistance is attributed both to unidirectional magnetic anisotropy of the FM layer and its splitting into magnetically nonequivalent regions in the porous films. The origin of the observed phenomenon is associated with a local influence on the orientation of AFM magnetic moments by an adjacent ferromagnet.