Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial Cosmic Microwave Background (CMB) and thereby induces new, small-scale B -mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even-and odd-parity E -and B -mode polarization mapped over ∼ 30 square degrees of the sky measured by the Polarbear experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B -modes is found at 4.2σ (stat.+sys.) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda Cold Dark Matter (ΛCDM) cosmological model. This measurement demonstrates 2 a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B -mode signal in searches for primordial gravitational waves.Introduction: As Cosmic Microwave Background (CMB) photons traverse the Universe, their paths are gravitationally deflected by large-scale structures. By measuring the resulting changes in the statistical properties of the CMB anisotropies, maps of this gravitational lensing deflection, which traces large-scale structure, can be reconstructed. Gravitational lensing of the CMB has been detected in the CMB temperature anisotropy in several ways: in the smoothing of the acoustic peaks of the temperature power spectrum [1-3], in cross-correlations with tracers of the large-scale matter distribution [4][5][6][7][8][9][10], and in the four-point correlation function of CMB temperature maps [11][12][13][14].The South Pole Telescope (SPT) collaboration recently reported a detection of lensed polarization using the cross-correlation between maps of CMB polarization and sub-mm maps of galaxies from Herschel/SPIRE [15]. A companion paper to this one has also shown the evidence of the CMB lensing-Cosmic Infrared Background crosscorrelation results using Polarbear data [16], finding good agreement with the SPT measurements. This crosscorrelation is immune to several instrumental systematic effects but the cosmological interpretation of this measurement requires assumptions about the relation of submm galaxies to the underlying mass distribution [17].In this Letter, we present the first direct evidence for gravitational lensing of the polarized CMB using data from the Polarbear experiment. We present power spectra of the lensing deflection field for two four-point estimators using only CMB polarization data, and tests for spurious systematic contamination of these estimators. We combine the two estimators to increase the signal-to-noise of the lensing detection.CMB lens...

We use time-resolved x-ray diffraction and magneto-optical Kerr effect to study the laser-induced antiferromagnetic to ferromagnetic phase transition in FeRh. The structural response is given by the nucleation of independent ferromagnetic domains (τ(1)~30 ps). This is significantly faster than the magnetic response (τ(2)~60 ps) given by the subsequent domain realignment. X-ray diffraction shows that the two phases coexist on short time scales and that the phase transition is limited by the speed of sound. A nucleation model describing both the structural and magnetic dynamics is presented.

We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the Polarbear experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < < 2100 and is based on observations of an effective sky area of 25 deg 2 with 3. 5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A BB to the measured band powers, A BB = 1.12 ± 0.61(stat) +0.04 −0.12 (sys) ± 0.07(multi), where A BB = 1 is the fiducial wmap-9 ΛCDM value. In this expression, "stat" refers to the statistical uncertainty, "sys" to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and "multi" to the calibration uncertainties that have a multiplicative effect on the measured amplitude A BB .

A spin reorientation accompanying the temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) phase transition is reported in strained epitaxial FeRh thin films. (57)Fe conversion electron Mössbauer spectrometry showed that the Fe moments have different orientations in FeRh grown on thick single-crystalline MgO and in FeRh grown on ion-beam-assist-deposited (IBAD) MgO. It was also observed, in both samples, that the Fe moments switch orientations at the AFM to FM phase transition. Perpendicular anisotropy was evidenced in the AFM phase of the film grown on IBAD MgO and in the FM phase of that grown on regular MgO. Density-functional theory calculations enabled this spin-reorientation transition to be accurately reproduced for both FeRh films across the AFM-FM phase transition and show that these results are due to differences in strain.

FeRh undergoes an unusual antiferromagnetic-to-ferromagnetic (AFM-FM) transition just above room temperature (T(AFM>FM)) that can be tuned or even completely suppressed with small changes in composition. The underlying temperature-dependent entropy difference between the competing AFM and FM states that drives this transition is measured by specific heat as a function of temperature from 2 to 380 K on two nearly equiatomic epitaxial Fe-Rh films, one with a ferromagnetic ground state (Fe-rich) and the other with an antiferromagnetic ground state (Rh-rich). The FM state shows an excess heat capacity near 100 K associated with magnetic excitations that are not present in the AFM state. The integrated entropy and enthalpy differences between the two alloys up to T(AFM>FM) agree with the previously measured entropy of the transition (ΔS = 17 ± 3 J/kg/K) and yield a T=0 energy difference of 3.4 J/g, consistent with literature calculations and experimental data; this agreement supports the use of the Fe-rich FM sample as a proxy for the (unstable) FM state of the AFM Rh-rich sample. From the low-temperature specific heat, along with sound velocity and photoemission measurements, the lattice contribution to the difference (ΔS(latt) = -33 ± 9 J/kg/K) and electronic contribution (ΔS(el) = 8 ± 1 J/kg/K) to the difference in entropy are calculated, from which the excess heat capacity in the FM phase and the resulting entropy difference are shown to be dominated by magnetic fluctuations (ΔS(mag) = 43 ± 9 J/kg/K). The excess magnetic heat capacity is dominated by the magnetic heat capacity of the FM phase, which can be fit to a Schottky-like anomaly with an energy splitting of 16 ± 1 meV and a multiplicity of 1 per unit cell.