Spontaneous Zero-Field Cooling Exchange Bias in Ni–Co–Mn–Sn Metamagnetic Heusler Sputtered Film

Metamagnetic off-stoichiometric Heusler alloys are actively being investigated because of their great potential as magnetocaloric materials. These properties are intimately related to the nanoscale homogeneity of their magnetic properties, mainly due to a strong influence of the nature of the exchange interactions between Mn atoms on the magnetism of the alloys. In this work, a spontaneous exchange bias phenomenon on a Ni–Co–Mn–Sn metamagnetic Heusler sputtered film is presented and studied in detail. More particularly, a series of DC magnetization curves measured as a function of the temperature demonstrates that the system exhibits canonical spin glass-like features. After a careful study of the field-cooling and zero-field-cooling curves measured on this system, the existence of magnetic inhomogeneities is inferred, as a consequence of the competition between ferromagnetic and antiferromagnetic exchange interactions between Mn atoms. Further AC susceptibility measurements on this system demonstrate that the underlying exchange bias phenomenon can be attributed to a magnetic clusters model based on superferromagnetic-like interactions present in the film. These findings suggest that the spontaneous exchange bias exhibited by the studied system is a consequence of the formation of this superferromagnetic-like state.

Influence of γ – radiation on the properties of silicon with clusters impurity atoms of manganese and nickel

In works [1-4], it was shown that a number of new physical phenomena are observed in silicon with nanoclusters, such as high-temperature negative magnetoresistance (NMR), anomalously high impurity photoconductivity, giant residual photoconductivity, etc. All these phenomena are directly related to the presence of multiply charged, magnetic clusters of manganese atoms in the silicon lattice. It is shown that, on the basis of such materials, it is possible to create fundamentally new, highly sensitive magnetosensors, photodetectors of infrared radiation operating in the μm region and photomagnetic devices.

High performance magnetorheological fluids: very high magnetization FeCo-Fe3O4 nanoclusters in ferrofluid carrier

High magnetization Fe3O4/OA-FeCo/Al2O3 nanocomposite magnetic clusters have been obtained by a modified oil-in-water miniemulsion method. These nanocomposite clusters dispersed in a ferrofluid carrier results in a magnetorheological fluid with improved...

Computer Simulation of Small Magnetic Clusters of 3d-Transition Metals of the Iron Subgroup Using the Hybrid Density Functional Method

This paper presents the results of s study focused on the stability of small 3d-transition-metal magnetic clusters (metals of an iron subgroup) in spin-polarized states using the hybrid density functional method. Computer modeling and full variational optimization of geometric structures of clusters were performed for various values of the spin multiplicity of electronic states. The binding energies, the bond lengths, and the frequencies of atomic zero-point vibrations in small clusters with a nuclearity of n = 2, 3, 4, 5, 6 were calculated depending on the metal (Fe, Co, Ni) and spin multiplicity M in the zero-charge state. The calculations were carried out using the hybrid density functional B3LYP method in the def2-TZVP basis set of the ORCA package algorithms. A comparison of the calculated results with the available experimental data is presented. It is shown that the calculated data obtained by the hybrid density functional method are in satisfactory agreement with the experimental data for “naked” clusters in inert media both for the spin multiplicity of the ground state and for the energy of atomic shock dissociation of clusters in inert gas flows.

Enhancement of Diversity in Production and Application Utilizing Electrolytically Polymerized Rubber Sensors with MCF: 1st Report on Consummate Fabrication Combining Varied Kinds of Constituents with Porous Permeant Stocking-Like Rubber

To satisfy the requirement of haptic sensibility in rubber such as in the proposed hybrid skin (H-Skin), the authors have demonstrated a new method for solidifying rubber using electrolytic polymerization together with configured magnetic clusters of magnetic compound fluid (MCF) incorporated into the rubber by the application of a magnetic field. However, the rubber and magnetic fluid (MF) involved in the MCF rubber were water-soluble. In addition, the authors have demonstrated the practicability of using electrolytic polymerization with an emulsifier, polyvinyl alcohol (PVA), in which natural rubber (NR) or chloroprene rubber (CR) and silicone rubber (Q) can be mixed as water-soluble and water-insoluble rubbers, respectively. In this study, to enhance production, the feasibility of solidifying rubber by electrolytic polymerization is verified using varied water-insoluble rubber, varied water-insoluble MF, and varied surfactants to aid emulsion polymerization, except in the case of other kinds of rubber and MF which have been demonstrated until recent by the authors. Based on these diverse constituents, the authors propose a consummate fabrication process for multi-layered MCF rubber, which involves porous stocking-like rubber that can be permeated by any liquid. The investigation of this application is presented in the sequential second report.

Magnetic Excitations

In this chapter, the neutron inelastic scattering spectrum is calculated for a variety of magnetic systems. A number of isolated magnetic systems are considered, including single-ion crystal field and intermultiplet excitations, and magnetic clusters. Linear spin-wave theory, a method for calculating the collective spin dynamics in magnetically ordered systems, is outlined and applied to ferromagnets and antiferromagnets both with and without anisptropy. The Random Phase Approximation (RPA) method for the generalized susceptibility is presented and applied to calculate the spectrum of crystal field excitons in praseodymium. The nature of the spin excitations in itinerant magnets is described, and the generalized susceptibility is calculated in the RPA for itinerant electrons with echange correlations. General features of the spin dynamical response in quantum magnets are described, and illustrated by the magnetic spectra of quantum spin chains.