One-dimentional magnonic crystal as a medium with magnetically tunable disorder on a periodical lattice

We show that periodic magnetic nanostructures (magnonic crystals) represent an ideal system for studying excitations on disordered periodical lattices because of the possibility of controlled variation of the degree of disorder by varying the applied magnetic field. Ferromagnetic resonance (FMR) data collected inside minor hysteresis loops for a periodic array of Permalloy nanowires of alternating width and magnetic force microscopy images of the array taken after running each of these loops were used to establish convincing evidence that there is a strong correlation between the type of FMR response and the degree of disorder of the magnetic ground state. We found two types of dynamic responses: anti-ferromagnetic (AFM) and ferromagnetic (FM), which represent collective spin wave modes or collective magnonic states. Depending on the history of sample magnetization either AFM or FM state is either the fundamental FMR mode or represents a state of a magnetic defect on the artificial crystal. A fundamental state can be transformed into a defect one and vice versa by controlled magnetization of the sample.Comment: 4 pages, 3 figures, Letter paper, already submitted to PR

Brillouin light scattering studies of planar metallic magnonic crystals

The application of Brillouin light scattering to the study of the spin-wave spectrum of one- and two-dimensional planar magnonic crystals consisting of arrays of interacting stripes, dots and antidots is reviewed. It is shown that the discrete set of allowed frequencies of an isolated nanoelement becomes a finite-width frequency band for an array of identical interacting elements. It is possible to tune the permitted and forbidden frequency bands, modifying the geometrical or the material magnetic parameters, as well as the external magnetic field. From a technological point of view, the accurate fabrication of planar magnonic crystals and a proper understanding of their magnetic excitation spectrum in the GHz range is oriented to the design of filters and waveguides for microwave communication systems

Collective spin waves in arrays of Permalloy nanowires with single-side periodically modulated width

We have experimentally and numerically investigated the dispersion of collective spin waves prop-agating through arrays of longitudinally magnetized nanowires with periodically modulated width. Two nanowire arrays with single-side modulation and different periodicity of modulation were studied and compared to the nanowires with homogeneous width. The spin-wave dispersion, meas-ured up to the third Brillouin zone of the reciprocal space, revealed the presence of two dispersive modes for the width-modulated NWs, whose amplitude of magnonic band depends on the modula-tion periodicity, and a set of nondispersive modes at higher frequency. These findings are different from those observed in homogeneous width NWs where only the lowest mode exhibits sizeable dis-persion. The measured spin-wave dispersion has been satisfactorily reproduced by means of dynam-ical matrix method. Results presented in this work are important in view of the possible realization of frequency tunable magnonic device

Granite Dusts and Poultry Manure Effects on Growth Performance and Yield of Maize (Zea Mays L.)

Poultry manure is rich in organic manure since solid and liquid wastes are excreted together and there is no urine loss. Comparative studies of the effects of various rates of granite dust and poultry manure were tested on maize performance in field trials at Akure, Nigeria between 2011 and 2012 cropping seasons.  The treatments involved were: Control(No treatment application), 2tha1 granite dust; 3tha1 poultry manure + 0.5tha1 granite dust; 2tha1 poultry manure + 1tha1 granite dust; 1tha1 poultry manure+ 1.5tha1 granite dust; 4tha1 poultry manure and 200kgha1 of NPK fertilizer. Agronomic parameters observed on maize at 2, 4, 6, 8, 10 and 12weeks after planting were plant height, stem girth, number of leaves.  At harvest, cob weight, plant biomass, grains weight per cob and husk weight were also measured. Equally, the ratio of root to stem and leaf of maize were investigated. It was found out that application combined application of granite dust and poultry manure improved the growth and yield quality of maize compared with the control. Maize treated with 3tha1 poultry manure + 0.5tha1 granite dust promote the growth and yield parameter of maize  to a level of the standard recommended fertilizer rate of 200kgha1 of NPK fertilizer in the ecological zone of the southwestern Nigeria. Keywords: Poultry manure, granite dusts, agronomic parameters, ratio, promote

Influence of Mycorrhizae and Rhizobium Inoculation on Growth, Nutrient Uptake and Proximate Composition of Upland Rice Cultivars

The activities of microbial rhizospheric organisms have been well documented in non-leguminous plants such as wheat, rice and maize. Such activities include nitrogen fixation, phosphate solubilization and mineralization that are beneficial for the overall growth and development of the plant. Field experiments were carried out in the early and late cropping season of 2013 in the tropical rainforest agro-ecology of southwest Nigeria to study the growth promotion, nutrient uptake, proximate composition of upland rice and harvested grains based on single inoculation of Mycorrhizae and Rhizobium. A 5 x 3 factorial experiment was conducted; five upland rice varieties selected with and without the application of mycorrhizae and rhizobium, laid out in split plot arrangement, with mycorrhizae and rhizobium in the main block, while variety was in the sub-plot. Each treatment was replicated three times. In both seasons, result show significant (P < 0.05) effect of single mycorrhizae and rhizobium inoculation on plant growth (plant height, numbers of tillers and leaves) and plant biomass except for shoot weight in the late season. Also, result show significant (P < 0.05) effect of single mycorrhizae and rhizobium inoculation on nutrient uptake in both seasons. Significant (P < 0.05) effect of single mycorrhizae and rhizobium inoculation was observed in proximate composition of rice grains in the early season, with rhizobium inoculated rice having the highest protein content. It was concluded that upland rice inoculation with mycorrhizae and rhizobium  improved their nutrient uptake, proximate composition and growth. Keywords: Mycorrhizae, rhizobium, upland rice, nutrient uptake, growth, proximate compositio

Magnetotransport properties of lithographically defined lateral Co/Ni80Fe20 wires

In this article we have investigated the magnetization reversal process of laterally defined coupled magnetic structures consisting of micron-sized sputtered Co and Ni80Fe20 wires lying side by side at temperatures ranging from 3 to 300 K. We have used a microfabrication technique to create an array of planar, laterally coupled magnetic wires made of two ferromagnetic materials. We observed two distinct peaks in the magnetoresistance (MR) curves corresponding to the magnetization reversals of Co and Ni80Fe20 wires. Below a critical temperature of 20 K we observed an asymmetric shift in the Ni80Fe20 peak position for both forward and reverse field sweeps due to the exchange coupling between the ferromagnetic (Ni80Fe20) and antiferromagnetic (Co–oxide at the interface of Co and Ni80Fe20 formed during fabrication) parts. The Co peaks gradually disappeared as the temperature was reduced. At low temperature we also observed that the Ni80Fe20 peaks in the MR loops are considerably shifted to larger fields corresponding to the increase in coercivity