The Origin of Tunneling Anisotropic Magnetoresistance in Break Junctions

First-principles calculations of electron tunneling transport in Ni and Co break junctions reveal strong dependence of the conductance on the magnetization direction, an effect known as tunneling anisotropic magnetoresistance (TAMR). The origin of this phenomenon stems from resonant states localized in the electrodes near the junction break. The energy and broadening of these states is strongly affected by the magnetization orientation due to spin-orbit coupling, causing TAMR to be sensitive to bias voltage on a scale of a few mV. Our results bear a resemblance to recent experimental data and suggest that TAMR driven by resonant states is a general phenomenon typical for magnetic broken contacts and other experimental geometries where a magnetic tip is used to probe electron transport.Comment: 4 pages, 3 figure

Structural stabilities, elastic constants, generalized stacking fault energetics, and the martensitic transformation mechanisms for the Ni50−xTiPtx (x = 0 − 30) ternary system: ab initio investigation

To determine the effect of ternary additions on the martensitic behavior of NiTi, we apply ab initio calculations using the highly precise full-potential linearized augmented plane wave method to the Ni-Ti-Pt system. We compare formation energies of various stoichiometries and the pair energetics between Pt atoms to create a numb er of model austenite structures, finding that Pt atoms prefer to decorate the lattice at third nearest neighbors from one another, and establish the hierarchy among the austenitic and martensitic phases. We examine the structural stability to determine the susceptibility toward displacive phase transformation: namely, we calculate planar generalized stacking fault energetics of major shear planes including the {100}, {011}, and {111} planes and we calculate and compare the elastic constants of each phase. We show that increased Pt content causes a dramatic softening of the austenite C′ elastic constant and increased rigidity in the martensite, and there is a high resistance to {100} shear similar to equiatomic NiTi. Finally, we explore a martensitic mechanism of this alloy and explain how the transformation path and energy barriers of the NiTi system are affected by Pt

Features of temperature dependence of contact resistivity in ohmic contacts on lapped n-Si

The temperature dependence of contact resistivity rho(c) in lapped silicon specimens with donor concentrations of 5 x 10(16), 3 x 10(17), and 8 x 10(17) cm(-3) was studied experimentally. We found that, after decreasing part of the rho(c)(T) curve in the low temperature range, an increasing part is registered with increasing temperature T. It is demonstrated that the formation of contact to a lapped Si wafer results in the generation of high dislocation density in the near-surface region of the semiconductor and also in ohmic contact behavior. In this case, current flows through the metal shunts associated with dislocations. The theory developed is in good agreement with experimental results. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752715