Ni3TeO6 - a collinear antiferromagnet with ferromagnetic honeycomb planes

We report a comprehensive study of magnetic properties of Ni3TeO6. The system crystallizes in a noncentrosymmetric rhombohedral lattice, space group R3. There are three differently coordinated Ni atoms in the unit cell. Two of them form an almost planar honeycomb lattice, while the third one is placed between the layers. Magnetization and specific heat measurements revealed a single magnetic ordering at TN = 52 K. Below TN the susceptibility with the magnetic field parallel to the c-axis drops towards zero while the perpendicular susceptibility remains constant, a characteristic of antiferromagnetic materials. Neutron diffraction confirmed that the system is antiferromagnet below TN with ferromagnetic ab-planes stacked antiferromagnetically along the c-axis. All Ni moments are in the S = 1 spin state and point along the c-axis.Comment: accepted for publication in Journal of Physics Condensed Matte

Modeling of Microwave Absorption Mechanisms in Metallic Powders

The microwave processing in powder metallurgy has only been under focus since the pioneering work of Roy and coworkers in 1999. The combination of the electromagnetic simulations using the Finite Integration Technique (FIT) and the extraction of effective properties can be used with success in the field of material science. The simulations over a wide range of frequency show a resonant behavior in the effective magnetic permeability of copper powders. The resonance frequency depends on the particle size and the conductivity of the material

Development of a claw pole permanent magnet motor with a molded low-density soft magnetic composite stator core

SMC (soft magnetic composite) materials and SMC electrical machines have undergone significant development in the past decade. For the molding of the SMC core, if a high productivity low pressure press is used, the manufacturing cost can be dramatically reduced. However, the magnetic properties of the SMC core and the machine performance are highly dependant on the mass density of the core. This paper presents the development of a claw pole permanent magnet motor with a low mass density SMC stator core molded at low pressure which can replace the existing single phase induction motor in a dish washer pump. The developed SMC motor has been prototyped and tested. Both the parameter computation and performance prediction are validated by the experimental results. These show that the low mass density SMC core is suitable for low cost mass production of SMC electrical machines. © 2009 IEEE

Index to NASA Tech Briefs, January - June 1967

Technological innovations for January-June 1967, abstracts and subject inde

Electrical and electronic devices and components: A compilation

Components and techniques which may be useful in the electronics industry are described. Topics discussed include transducer technology, printed-circuit technology, solid state devices, MOS transistors, Gunn device, microwave antennas, and position indicators

Consortium for materials development in space

The status of the Consortium for Materials Development in Space (CMDS) is reviewed. Individual projects are outlined and the status of Get Away Special (GAS) 105 is summarized

Low dimensional magnetic solids and single crystal elpasolites: Need for improved crystal growing techniques

The need for extensive crystal growing experiments to develop techniques for preparing crystals suitable for magnetic anisotropy measurements and detailed X-ray and neutron diffraction studies is rationalized on the basis of the unique magnetic properties of the materials and their hydrogen bonded structures which have many features in common with metalloenzyme and metalloprotein active sites. Single crystals of the single and mixed lanthanide species are prepared by the Bridgeman technique of gradient solidification of molten samples. The effects of crystal imperfections on the optical properties of these materials are an important part of the projected research. A series of a-amido acid complexes of first row transition metals were prepared which crystallize as infinite linear chains and exhibit low dimensional magnetic ordering (one or two) at temperature below 40 K

Magnetic fluctuations and superconductivity in Fe pnictides probed by electron spin resonance

The electron spin resonance absorption spectrum of Eu^{2+} ions serves as a probe of the normal and superconducting state in Eu_{0.5}K_{0.5}Fe_2As_2. The spin-lattice relaxation rate 1/T_1^{\rm ESR} obtained from the ESR linewidth exhibits a Korringa-like linear increase with temperature above T_C evidencing a normal Fermi-liquid behavior. Below 45 K deviations from the Korringa-law occur which are ascribed to enhanced magnetic fluctuations within the FeAs layers upon approaching the superconducting transition. Below T_C the spin-lattice relaxation rate 1/T_1^{\rm ESR} follows a T^{1.5}-behavior without the appearance of a coherence peak.Comment: 5 pages, 5 figure