arXiv subjects

B. Richard

Publications and source records attributed to B. Richard.

3 recordsLinked to original sources

arXiv2019

A Spinodal Solution to Swampland Inflationary Constraints

We show how the inclusion of non-perturbative, {\em dynamical} quantum effects on the evolution of the inflaton can allow for an inflationary phase that is both consistent with cosmological constraints {\em and} avoids the problems associated with the so-called swampland conditions. In particular, for concave potentials such as those preferred by the Planck data, spinodal instabilities associated with tachyonic masses for long wavelength modes induce a second round of inflation, which in essence decouples the tree-level potential from the inflationary phase. We illustrate these points using natural inflation as an example.

hep-th↗

arXiv2010

Conduction Electron Scattering and Spin-Flipping at Sputtered Co/Ni Interfaces

Current-perpendicular-to-plane magnetoresistance (CPP-MR) measurements let us quantify conduction electron scattering and spin-flipping at a sputtered ferromagnetic/ferromagnetic (F1/F2 = Co/Ni) interface, with important consequences for CPP-MR and spin-torque experiments with perpendicular anisotropy. We use ferromagnetically coupled ([Ni/Co]xn)Ni multilayers, and Py-based, symmetric double exchange-biased spin-valves (DEBSVs) containing inserts of ferromagnetically coupled ([Co/Ni]xn)Co or ([Ni/Co]xn)Ni multilayers, to derive Co/Ni interface specific resistances AR(Co/Ni)(Up) = 0.03 (+0.02)(-0.03) f-ohm-m^2 and AR(Co/Ni)(down) = 1.00 +/- 0.07 f-ohm-m^2, and interface spin-flipping parameter delta(Co/Ni) = 0.35 +/- 0.05. The specific resistances are consistent with our no-free-parameter calculations for an interface thickness between 2 and 4 monolayers (ML) that is compatible with expectations.

cond-mat.mtrl-sci↗

arXiv2008

Spin-Diffusion Lengths in Dilute Cu(Ge) and Ag(Sn) Alloys

We use current-perpendicular-to-plane (CPP) exchange-biased spin-valves to directly measure spin diffusion lengths lsf for N = Cu(2.1 at.%Ge) and Ag(3.6 at.%Sn) alloys. We find lsf(Cu2%Ge)) = 117+10-6 nm and lsf(Ag4%Sn)= 39 +/- 3 nm. The good agreement of this lsf(Cu2%Ge) with the value lsf(Cu2%Ge) = 121 +/- 10 nm derived from an independent spin-orbit cross-section measurement for Ge in Cu, quantitatively validates the use of Valet-Fert theory for CPP-MR data analysis to layer thicknesses several times larger than had been done before. From the value of lsf(Ag4%Sn), we predict the ESR spin-orbit cross-section for Sn impurities in Ag.

cond-mat.mtrl-sci↗