Recently, spin-charge conversion induced magnetoresistance (MR) in a ferromagnet (FM) or its junction with a heavy metal (HM) has attracted great attention due to its potential applications in spintronics as well as being a powerful technique for studying spin-charge interaction and transport in magnetic thin films and heterostructures. In this talk, I will discuss our recent finding of an MR induced by the anomalous Hall effect (AHE) in a ferromagnet . When a charge current flows in a ferromagnet, both transverse charge and spin accumulations will occur at boundaries of the sample at steady state. The spin accumulation in turn induces a spin current either in an adjacent material or in the ferromagnet itself due to backflow of spin from the boundary. We demonstrate that the spin accumulation, subsequent spin backflow, and spin-charge conversion can give rise to a different type of spin current related magnetoresistance, dubbed as the anomalous Hall magnetoresistance (AHMR), which has the same angular dependence as the recently discovered spin Hall magnetoresistance (SMR). The AHMR is observed in four types of samples: co-sputtered (Fe1-xMnx)0.6Pt0.4, Fe1-xMnx/Pt multilayer, Fe1-xMnx with x = 0.17 – 0.65 and Fe, and analyzed using the drift-diffusion model. The AHMR provides an alternative route to study charge-spin conversion in ferromagnets and to exploit it for potential spintronic applications. In addition to AHMR, I will also discuss spin-torque induced by AHE in both single layer and multilayer structures and its applications in magnetization switching.
A 100 watt and ytterbium doped fiber laser based on MOPA structure is reported in this paper. The laser uses a modulated semiconductor laser as the seed source with pulse width of 10-350 ns and repetition frequency continuously adjustable in the range of 90 kHz-1100 kHz. Using 30/250μm large mode area fiber, the stable nanosecond pulse width is obtained by setting the optimum fiber length of 6 m. The second stage main amplifier uses 6 30W pumps, and the reverse-pump mode. When the repetition rate is 90 K Hz, the average power output of 100 W is obtained by the main power amplifier (MOPA). At the highest output power, due to gain shaping mechanism, the pulse width is reduced from 375 ns to 350 ns. The corresponding peak power is 10 kW, the single pulse energy is 1.11 mJ, and the output signal-to-noise ratio reaches 36 dB at the highest output power. And at the moment, the SRS effect happens just at the center wavelength 60NM. In this paper, a tunable 100-watt nanosecond fiber laser with two-stage amplification based on semiconductor modulation technology is presented. A compact 100W prototype has been completed.
2kW single-mode fiber laser with two cascade home-made cladding light strippers (CLSs) by employing bidirectionalpump scheme has been demonstrated. 2.009 kW signal power is obtained when pump power is 2.63 kW and the slope efficiency is 76.6%. Raman Stokes light is less than -47 dB at 2.009 kW even with a 10-m delivery fiber with core/inner cladding diameter of 20/400um. The beam quality M2≤1.2 and the spectral FWHM bandwidth is 4.34nm. There is no transverse mode instability and the output power stability of ±0.14% is achieved by special thermal management for a more uniform temperature distribution on the Yb-doped gain fiber.