From magnetic, dielectric and magnetoelectric measurement, it is concluded that hexagonal HoMnO 3 , ErMnO 3 and YbMnO 3 undergo a magnetic phase transition at a low temperature where a magnetic longrange order of rare earth ions is established. Possible magnetic structures are estimated from the experimental results and symmetry consideration. This low-temperature phase transforms successively into possibly two different phases in magnetic field. The higher-field phase is considered to have a ferrimagnetic arrangement of the rare earth magnetic moments.

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Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 1018 W cm−2, the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines.

Articles you may be interested inSynchronized time-and high-field-resolved all-optical pump-probe magneto-optical setup based on a strong alternating magnetic field and its application in magnetization dynamics of high coercivity magnetic medium Rev. Sci. Instrum. 82, 034703 (2011); 10.1063/1.3565156Field-dependent ultrafast dynamics and mechanism of magnetization reversal across ferrimagnetic compensation points in GdFeCo amorphous alloy films Submicron-scale spatial feature of magnetization reversal dynamics induced by femtosecond optical pulse irradiation in a small external magnetic field was investigated by time-resolved magneto-optical Kerr microscopy on TbFeCo thin film. The magnetization reversal time near the magnetic domain boundary is dominated by an effective magnetic field generated from the peripheral domain by dipole-dipole interaction. The magnetization reversal is accelerated as high as 4.5 times ͑from 3.4 ns to 750 ps͒ when reducing the reversed domain size from 1.5 to 0.4 m due to concentration of dipole-dipole interaction.

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Fast isochoric heating of a pre-compressed plasma core with a high-intensity short-pulse laser is an attractive and alternative approach to create ultra-high-energy-density states like those found in inertial confinement fusion (ICF) ignition sparks. Laser-produced relativistic electron beam (REB) deposits a part of kinetic energy in the core, and then the heated region becomes the hot spark to trigger the ignition. However, due to the inherent large angular spread of the produced REB, only a small portion of the REB collides with the core. Here, we demonstrate a factor-of-two enhancement of laser-to-core energy coupling with the magnetized fast isochoric heating. The method employs a magnetic field of hundreds of Tesla that is applied to the transport region from the REB generation zone to the core which results in guiding the REB along the magnetic field lines to the core. This scheme may provide more efficient energy coupling compared to the conventional ICF scheme.

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