The interfacial spin state of the multiferroic heterostructure PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3 and its dependence on ferroelectric polarization is investigated with magnetic second-harmonic generation at 78 K. The spin alignment of Mn ions in the first unit cell layer at the heterointerface can be tuned from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. Multiple domains of both phases coexist as the ferroelectric polarization is switched. The results will help promote the development of new interface-based functionalities and device concepts. The work at College of William and Mary was supported by the Department of Energy (Grant No. DE-FG02-04ER46127). The work at University of Puerto Rico was supported by the Grant No. DE-FGD2-08ER46526. The work at Fudan University was supported by the National Natural Science Foundation of China (Grant No. 61222407).

The light reflection oscillations resulting from the coherent scattering of polariton states and propagating coherent acoustic phonons (CAPs) in a ZnO single crystal are studied by using a two-color femtosecond pump-probe technique. The oscillation frequency manifested in the photoinduced reflectance shows a nonlinear dependence on the probe-beam wave vector owing to the variation of the refractive index near the band gap. The oscillation amplitude is affected by the refractive index modulation derived from the CAP-detuning polariton states. The larger oscillation for shorter probe-beam wavelengths is consistent with the stronger scattering between the CAP and excitonlike polariton states closer to the band gap.

The dependence of perpendicular magnetic anisotropy Ku on spin-orbit coupling strength ξ is investigated in L10 ordered FePd1−xPtx films by time-resolved magneto-optical Kerr effect measurements and ab initio density functional calculations. Continuous tuning of Ku over a wide range of magnitude is realized by changing the Pt/Pd concentration ratio, which strongly modifies ξ but keeps other leading parameters affecting Ku nearly unchanged. Ab initio calculations predict a nearly quadratic dependence of Ku on ξ, consistent with experimental data. Ku increases with increasing chemical order and decreasing thermal spin fluctuations, which becomes more significant for samples with higher Pt concentration. The results demonstrate an effective method to tune Ku utilizing its sensitivity on ξ, which will help fabricate magnetic systems with desirable magnetic anisotropy. The TR-MOKE experiments, data analysis, and discussions performed at the College of William and Mary were sponsored by DOE through Grant No. DE-FG02-04ER46127. H.Z. acknowledges financial support from National Natural Science Foundation of China (Grant Nos. 61222407 and 51371052) and NCET (No. 11-0119). G.Y.G. thanks the National Science Council of Taiwan for financial supports.

The temperature dependence of the Gilbert damping and magnetic anisotropy are investigated in L21 Co2FeAl films epitaxially grown on GaAs (001) substrate by the time resolved magneto-optical Kerr effect. We found that the in-plane biaxial anisotropy increases by more than 90% with the temperature decreasing from 300 K to 80 K, which is mainly due to the strong variation of the magneto-elastic coefficients. In contrast, the intrinsic Gilbert damping rises only about 10%, which is mainly attributed to the reduction of the electron phonon scattering rate, independent of the strain-induced spin-orbit coupling energy. This work was supported by the National Natural Science Foundation of China with Grants Nos. 61222407 and 51371052, NCET (No. 11-0119), and MOST of China with Grants Nos. 2013CB922303 and 2011CB921801.

A class of polymers (POT-DH, POT-HCN and POT-DCN) were synthesized and they contain the same donor (BDT) and acceptor units but different numbers of cyano (CN)-groups, i.e. 0, 1 and 2. We investigated for the first time the effects of different CN-group numbers on the optoelectronic, molecule packing, film morphology and photovoltaic properties of three conjugated polymers. With increased CN-group number, broader absorption, smaller optical bandgap and lower HOMO level can be obtained. The planarity of polymers also decreases with increasing CN-groups, leading to different inter-molecular packing and morphology. The incorporation of two CN-groups results in poor morphology, inefficient charge transfer and very low device performance. Due to the optimized POT-HCN polymer possessing the most balanced properties, the best PCE of 4.21% was demonstrated by POT-HCN with one CN-group. Thus we believe that, by controlling the number of introduced CN-groups, we can generally fine-tune the planarity and LUMO/HOMO levels of this class of polymers to achieve desired optoelectronic properties and morphology for high photovoltaic performance. This also provides a feasible way for optimizing other photovoltaic semiconducting polymers by adjusting the number of electron-withdrawing units.