In this study,aberration-corrected scanning transmission electron microscopy coupled with electron energy-loss spectroscopy(STEM-EELS)was used to investigate the atomistic structure and chemical com-position of true t...In this study,aberration-corrected scanning transmission electron microscopy coupled with electron energy-loss spectroscopy(STEM-EELS)was used to investigate the atomistic structure and chemical com-position of true twin and order twin boundaries in ferromagneticτ-MnAl-C.True twins and order twins were distinguished based on the diffraction patterns using TEM.No elemental segregation was observed at the coherent true twin boundary but some Mn enrichment within a region of about 1.5-2 nm was found at the incoherent true twin boundary.A transition region with Mn enrichment about 4-6 nm wide was found at the order twin boundary.A carbon cluster with a size of around 5 nm was also found at the twin boundary.Micromagnetic simulations were conducted to study the effect of this chemical seg-regation at twin interfaces on the magnetic properties.The results showed that the coercivity tends to increase with increasing structural and chemical disorder at the interface.展开更多
Surface phonon polaritons(SPhPs)exhibit promising advantages(e.g.,low loss,long lifetimes)for mid/far-infrared(MIR/FIR)nanophotonics.However,FIR SPhPs experiments remain challenging for conventional optics and scatter...Surface phonon polaritons(SPhPs)exhibit promising advantages(e.g.,low loss,long lifetimes)for mid/far-infrared(MIR/FIR)nanophotonics.However,FIR SPhPs experiments remain challenging for conventional optics and scatteringtype scanning near-field optical microscopy(s-SNOM)due to the lack of compatible light sources/detectors.In this work,we characterized~75-110 meV SPhPs in AlN nanowires using a monochromated scanning transmission electron microscope(STEM)equipped with electron energy loss spectroscopy(EELS).This technique provided exceptional 4.3 meV energy resolution and sub-angstrom spatial resolution.We observed the evolution of SPhP interference fringes with propagation distance,derived the dispersion curve,and clarified size effects on SPhP propagation by tuning AlN structure dimensions.Experimental-numerical cross-validation confirmed that the local continuum model(LCM)accurately describes AlN's SPhP behaviors.This work advances the understanding of FIR SPhPs in polar dielectrics and establishes a robust platform for studying FIR phonon polariton materials.展开更多
基金funded by the Deutsche Forschungsgemein-schaft(DFG,German Research Foundation,No.326646134)the Austrian Science Fund(FWF,No.Ⅰ3288-N36).
文摘In this study,aberration-corrected scanning transmission electron microscopy coupled with electron energy-loss spectroscopy(STEM-EELS)was used to investigate the atomistic structure and chemical com-position of true twin and order twin boundaries in ferromagneticτ-MnAl-C.True twins and order twins were distinguished based on the diffraction patterns using TEM.No elemental segregation was observed at the coherent true twin boundary but some Mn enrichment within a region of about 1.5-2 nm was found at the incoherent true twin boundary.A transition region with Mn enrichment about 4-6 nm wide was found at the order twin boundary.A carbon cluster with a size of around 5 nm was also found at the twin boundary.Micromagnetic simulations were conducted to study the effect of this chemical seg-regation at twin interfaces on the magnetic properties.The results showed that the coercivity tends to increase with increasing structural and chemical disorder at the interface.
基金supported by the National Key R&D Program of China(Grant No.2023YFB3609903)the National Natural Science Foundation of China(Grant Nos.52125307and 12404192)+1 种基金the“2011 Program”from the Peking–Tsinghua–IOP Collaborative Innovation Center of Quantum Mattersupport from the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘Surface phonon polaritons(SPhPs)exhibit promising advantages(e.g.,low loss,long lifetimes)for mid/far-infrared(MIR/FIR)nanophotonics.However,FIR SPhPs experiments remain challenging for conventional optics and scatteringtype scanning near-field optical microscopy(s-SNOM)due to the lack of compatible light sources/detectors.In this work,we characterized~75-110 meV SPhPs in AlN nanowires using a monochromated scanning transmission electron microscope(STEM)equipped with electron energy loss spectroscopy(EELS).This technique provided exceptional 4.3 meV energy resolution and sub-angstrom spatial resolution.We observed the evolution of SPhP interference fringes with propagation distance,derived the dispersion curve,and clarified size effects on SPhP propagation by tuning AlN structure dimensions.Experimental-numerical cross-validation confirmed that the local continuum model(LCM)accurately describes AlN's SPhP behaviors.This work advances the understanding of FIR SPhPs in polar dielectrics and establishes a robust platform for studying FIR phonon polariton materials.
