Non-Volatile Memory Characteristics of Submicrometre Hall Structures Fabricated in Epitaxial Ferromagnetic MnAl Films on GaAs

Hall-effect structures with submicrometre linewidths (<0.3pm) have been fabricated in ferromagnetic thin films of Mn[sub 0.60]Al[sub 0.40] which are epitaxially grown on a GaAs substrate. The MnAl thin films exhibit a perpendicular remanent magnetisation and an extraordinary Hall effect with square hysteretic behaviour. The presence of two distinct stable readout states demonstrates the potential of using ultrasmall ferromagnetic volumes for electrically addressable, nonvolatile storage of digital information

The extraordinary Hall effect in coherent epitaxial tau (Mn,Ni)Al thin films on GaAs

Ultrathin coherent epitaxial films of ferromagnetic tau(Mn,Ni)0.60Al0.40 have been grown by molecular beam epitaxy on GaAs substrates. X-ray scattering and cross-sectional transmission electron microscopy measurements confirm that the c axis of the tetragonal tau unit cell is aligned normal to the (001) GaAs substrate. Measurements of the extraordinary Hall effect (EHE) show that the films are perpendicularly magnetized, exhibiting EHE resistivities saturating in the range of 3.3-7.1 muOMEGA-cm at room temperature. These values of EHE resistivity correspond to signals as large as +7 and -7 mV for the two magnetic states of the film with a measurement current of 1 mA. Switching between the two magnetic states is found to occur at distinct field values that depend on the previously applied maximum field. These observations suggest that the films are magnetically uniform. As such, tau(Mn,Ni)Al films may be an excellent medium for high-density storage of binary information

Epitaxial-tau(Mn,Ni)Al/(Al,Ga)As heterostructures: Magnetic and magneto-optic properties

Ferromagnetic Perpendicularly magnetized epitaxial thin films of tau (Mn,Ni)AI have been successfully grown on AlAs/GaAs heterostructures by molecular beam epitaxy. We have investigated the polar Kerr rotation and magnetization of tau MnAl and (Mn,Ni) Al as a function of Mn and Ni concentration. The largest polar Kerr rotation and remnant magnetization were obtained for Mn0.5Al0.5 thin films with values of 0.16-degrees and 224 emu/cm3, respectively. We observed that the Kerr rotation and magnetization remained constant with Ni additions up to about 12 at. % and subsequently decreased with further Ni additions. We discuss these results and one possible method of enhancing the Kerr rotation

Cobalt(II), nickel(II) and zinc(II) coordination chemistry of the N , N ′-disubstituted hydroxylamine-(diamido) ligand, 3,3′-(hydroxyazanediyl)dipropanamide

Although directly relevant to metal mediated biological nitrification and the coordination chemistry of peroxide, the transition metal complexes of hydroxylamines and their functionalized variants remain mainly unexplored except vanadium(V) and molybdenum(VI). Reaction of the chelating hydroxylamine ligand 3,3′-(hydroxyazanediyl)dipropanamide (Hhydia) with [MII(CH3COO)2]·xH2O (M = CoII, ZnII) in methyl alcohol solution yields the complexes [CoII(η1:η1-CH3COO)(η1-CH3COO)(Hhydia)], (1) and [ZnII(η1-CH3COO)2(Hhydia)], (4), while reaction of Hhydia with trans-[NiIICl2(H2O)4]·2H2O yields [NiII(Hhydia)2]Cl2 (3). The X-ray structure analysis of 1 and 4 revealed that the CoII and ZnII atoms are bonded to a neutral tridentate O,N,O-Hhydia ligand and a chelate and a monodentate acetate groups in a severely distorted octahedral geometry for 1 and two monodentate acetate groups for 4 in a highly distorted trigonal bipyramidal geometry (τ = 0.63). The X-ray structure analysis of 3 revealed that the nickel atom in [NiII(Hhydia)2]2+ is bonded to two neutral tridentate O,N,O-Hhydia ligands. The twist angle, θ, in [NiII(Hhydia)2]2+ is 55.1(2)°, that is, very close to an ideal octahedron. The metal/Hhydia complexes were studied by UV–Vis (cobalt and nickel compounds), NMR (zinc compounds), HR-MS spectroscopy. The 1H and 13C NMR spectra of the methyl alcohol or acetonitrile solutions of ZnII-Hhydia complexes show the existence of both the 1:1 and 1:2 metal:ligand species being in dynamic equilibrium. The exchange processes between the ZnII-Hhydia is through complete dissociation-association of the ligand from the complexes as it is evident from the 2D {1H} EXSY NMR spectroscopy. UV–Vis spectroscopy of the CoII-Hhydia in methyl alcohol also shows the existence of both the 1:1 and 1:2 metal:ligand species in contrast to 1:2 complex [NiII(Hhydia)2]2+ which is the only species found in solution. The NMR and UV–Vis observations are additionally supported by the HR-MS studies

Stress biomarker changes following a series of repeated static and dynamic apneas in non-divers

Purpose This study examined the magnitude of physiological strain imposed by repeated maximal static and dynamic apneas through assessing a panel of stress-related biomarkers. Methods Eleven healthy men performed on three separate occasions (≥72-h apart): a series of five repeated maximal (i) static (STA) or (ii) dynamic apneas (DYN) or (iii) a static eupneic protocol (CTL). Venous blood samples were drawn at 30, 90, and 180-min after each protocol to determine ischaemia modified albumin (IMA), neuron-specific enolase (NSE), myoglobin, and high sensitivity cardiac troponin T (hscTnT) concentrations. Results IMA was elevated after the apnoeic interventions (STA,+86%;DYN,+332%,p ≤ 0.047) but not CTL (p = 0.385). Myoglobin was higher than baseline (23.6 ± 3.9 ng/mL) 30-min post DYN (+70%,38.8 ± 13.3 ng/mL,p = 0.030). A greater myoglobin release was recorded in DYN compared with STA and CTL (p ≤ 0.035). No changes were observed in NSE (p = 0.207) or hscTnT (p = 0.274). Conclusions Five repeated maximal DYN led to a greater muscle injury compared with STA but neither elicited myocardial injury or neuronal-parenchymal damage

Electrocatalytic hydrogen production by dinuclear cobalt(ii) compounds containing redox-active diamidate ligands: a combined experimental and theoretical study

The chiral dicobalt(II) complex [CoII2(μ2-L)2] (1) (H2L = N2,N6-di(quinolin-8-yl)pyridine-2,6-dicarboxamide) and its tert-butyl analogue [CoII2(μ2-LBu)2] (2) were synthesized and structurally characterized. Addition of one equivalent of AgSbF6 to the dichloromethane solution of 1 and 2 resulted in the isolation of the mixed-valent dicobalt(III,II) species [CoIIICoII(μ2-L)2]SbF6 (3) and [CoIIICoII(μ2-LBu)2]SbF6 (4). Homovalent 1 and 2 exhibited catalytic activity towards proton reduction in the presence of acetic acid (AcOH) as the substrate. The complexes are stable in solution while their catalytic turnover frequency is estimated at 10 and 34.6 h−1 molcat−1 for 1 and 2, respectively. Calculations reveal one-electron reduction of 1 is ligand-based, preserving the dicobalt(II) core and activating the ligand toward protonation at the quinoline group. This creates a vacant coordination site that is subsequently protonated to generate the catalytically ubiquitous Co(III) hydride. The dinuclear structure persists throughout where the distal Co(II) ion modulates the reactivity of the adjacent metal site by promoting ligand redox activity through spin state switching